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Insanity Defense

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Rachel Dawes: This is the third of Falcone's thugs you've had declared insane... and moved into your asylum.
Dr. Jonathan Crane: Well, the work offered by organized crime must hold an attraction to the insane.

This is an affirmative defense in which it is claimed that the defendant in a criminal trial is or was unable to understand the nature or unlawfulness of their actions due to a mental defect or disorder, and thus not responsible for the consequences of those actions. "Insanity" here is a legal term, not a medical one, and the court decides whether it applies — though it will take the advice of medical professionals into account. (It's worth noting that having a mental illness, even a serious one, does not necessarily make an insanity defense valid; the dividing line is whether the person was able to understand that what they were doing is wrong. If they were, then they're legally sane regardless of their greater mental health status.)

While the use of insanity as a defense has been known since ancient times, it was codified in English law by the ruling in R. v M'Naghten in 1843, which were adopted shortly thereafter in other common-law jurisdictions (including the United States). Most countries in the modern world have some variation of the insanity defense available to criminal defendants. Some jurisdictions instead have "Guilty But Insane," where insanity cannot be a complete defense, but can be a mitigating factor.

In Real Life, the insanity plea is rare and difficult to succeed with. It is also a risky gamble since it is an affirmative defense that requires the defendant to concede culpability in the crime in question and places the burden of proof on the defense to prove beyond a reasonable doubt that their client was insane at the time they committed the crime. Perhaps one percent of criminal cases even attempt an insanity defense, and only about a quarter of those are accepted, primarily if the defendant already has a history of mental illness. Furthermore, it requires expert testimony from a reputable psychiatric authority that the defendant was insane at the time they committed the crime, not just insane in general. Naturally, since the insanity defense is dramatic, it is used much more often in fiction.

A variant is "Temporary Insanity," in which the defendant is claimed to have been suffering from an "irresistible impulse" during the crime, but is now sane. Thus, they can be released immediately, rather than being incarcerated for psychiatric treatment. This defense was first used in the United States by U.S. Congressman Daniel Sickles of New York in 1859, after murdering his wife's lover.note  It was most prevalent as a defense during the 1940s and '50s. Most states do not allow this defense today.

Along similar lines, the "Extreme Emotional Disturbance" defense argues mitigating factors compromised the defendant's ability to think rationally. For instance, a man who shot his wife after catching her in bed with her lover could argue his emotional state at the time makes him guilty of the lesser crime of Manslaughter and not 2nd-degree Murder.

Since someone who has been declared "Not Guilty By Reason of Insanity" is incarcerated for psychiatric treatment until they are deemed to be no longer a threat to themselves or others, this can result in a longer loss of freedom than a normal jail sentence would have caused. Because of this, a defendant has the right to insist that this defense not be used in their case. This has not stopped some defendants — both in fiction and in Real Life — going for this defense under the mistaken belief that a plea of 'insanity' means a cushier time than a regular jail sentence. Also, in some jurisdictions, such as the District of Columbia, a person found not guilty of a sex crime solely by reason of insanity or diminished capacity must register as a sex offender, as though that person had been convicted.

A Catch-22 Dilemma takes place with many juries: if the defendant is capable of understanding that an insanity plea would be a good idea, then perhaps they're not legally insane (as insane people typically don't know they're insane — note emphasis on typically, since some actually do know there's something wrong with them). This is in fact closely related to the original Catch-22; the dilemma discussed in that book that a serviceman who requests a discharge for insanity must be sane enough to think to do so, in which case he is refused one.

Another use of this trope common in fiction is for a floundering Amoral Attorney to switch to an insanity defense as a last resort, ignoring the real-life procedural steps needed for this action. It almost never works, just emphasizing how doomed the client is.

A related concept is fitness to stand trial. This is often confused with the insanity defense, particularly since they often apply to the same people, but fitness to stand trial says nothing about their mental state when they did the crime. It's about whether their current mental state allows them to understand the charges against them and conduct an appropriate defense. For example, a defendant who was clearly responsible for the crime he committed, but while awaiting trial suffers brain damage from a suicide attempt and becomes unfit to stand trial. Rather than going to jail, he's sent to a care facility. Should he ever recover enough to be declared fit, he will stand trial.

Another concept related to insanity, although rarely seen in media, is diminished capacity. Diminished capacity is a claim that the defendant was unable to form the mental state (intent, recklessness, negligence, etc.) required for their action to be a crime. Because diminished capacity is not an affirmative defense, but rather the negation of an element of the crime, the burden of proof remains on the prosecution. Additionally, a successful diminished capacity defense results in a verdict of "not guilty", rather than "not guilty by reason of insanity", so the defendant is not incarcerated for psychiatric treatment (unless the state begins civil commitment proceedings). As a result, diminished capacity tends to be preferred to the insanity defense in jurisdictions in which it is allowed (although the two can be, and often are, combined).

In the United States, neither psychopathy nor a personality disorder is generally accepted as grounds for an insanity plea, and most states will simply throw the perpetrator in jail like any other criminal if that is their mental illness, since though such persons may have the adequate Lack of Empathy that you can say they don't appreciate the moral reasons for why their crimes were wrong, in general they still understood that they were breaking the law, and having pathological justifications for doing so isn't good enough. However, other countries, such as the United Kingdom, do accept these as valid grounds, and many notorious British serial killers are locked up in mental institutions whereas in America they would be imprisoned for life or sentenced to death. Such British prisoners, however, are usually not expected to ever be released and most of their appeals fail. In fiction, many cases of the insanity defense are often based on personality disorders, even if they are American.


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    Anime and Manga 
  • A rare correct portrayal happens at the end of the Read or Die OVA. Most of the villains are killed except for Nancy's Evil Twin, who survives but is rendered brain-damaged and mentally ill after being drowned during the final battle. Since she's now incapable of caring for herself and has no memory of her past, she's declared mentally unfit to stand trial and remanded into state care… with the caveat that if she ever recovers then she'll be tried.
  • In Tokyo Babylon, Subaru encounters a woman who is trying to summon a dog spirit to kill the man who murdered her young daughter, since he had been deemed too insane to stand trial. She plans on using the insanity defense for herself afterwards, figuring that a judge would see the "attempted" ritual as proof that she had lost her mind before killing the man herself.

    Comic Books 
  • Batman:
    • Most of the inhabitants of Arkham Asylum for the Criminally Insane have had a successful Insanity Defense entered on their behalf. Many of them are also, not coincidentally, crazy. However, most of them are not legally insane by any reasonable interpretation. A pathological obsession with hats, cats, birds, or riddles does not mean someone isn't aware of what they're doing. The same goes for being an eco-terrorist, wanting to eat people, or most of the various eccentricities Batvillains develop while pursuing a criminal career. The vast majority of notable Batman villains are serial offenders who are fully aware that they are breaking the law and in many cases even brag about it, and several methodically and deliberately plan their crimes out- in other words, they know full well that they are committing crimes but they do it anyway.
    • A 2009 Comic Con panel of lawyers noted that nearly all of Batman's villains did not qualify, including Joker.
    • During the Golden Age and The Interregnum, The Joker was not considered insane enough to qualify for this defense. When he tried it, Batman easily proved that despite Joker's eccentricity, he was fully capable of understanding the illegality and consequences of his actions. It was only when the Joker became a homicidal maniac in the 1970s that Arkham Asylum became a necessity for him.
    • In The Joker: Devil's Advocate, a new D.A. decides to go for broke and push for the death penalty after a series of killings with the Joker's MO. After a "Trial of the Century" with accompanying media circus, he is found guilty and sentenced to death. However, he claims to have no knowledge of the murders. Batman, who has never known the Joker to deny any of his crimes, investigates and finds out that this time he really is innocent. Joker is returned to Arkham when this is revealed.
    • The nearly abusive use of this defense among Batman villains in particular has caused more than one rant from real legal professionals. It concluded that only Two-Face and sometimes The Joker are "legally" insane, though it's an old and incomplete list. For those who don't feel like reading the linked article in full, what the article concludes is that sometimes the Joker does appear to have a valid insanity defense for his actions (wrongfulness test: sometimes he literally doesn't think what he's doing is wrong; at other times he knows it's wrong but does it anyway For the Lulz, which is not a valid defense), and Two-Face pretty much always appears to have one (irresistible impulse test: he knows it's wrong, but can't stop himself because the coin came up scarred). It specifically lists those two as examples of Arkham inmates who probably do belong there; it then gives a (short) list of others that don't: the Scarecrow, the Mad Hatter, the Penguin, Poison Ivy, Tweedledum and Tweedledee. They don't exhibit any behavior compatible with the legal definition of insanity... mental illness, maybe; they're certainly eccentric... but they fail both prongs of the insanity definition: wrongfulness and irresistible impulse. The author explicitly mentions that he's not trying to give an exhaustive list either way, just examples so that readers can understand what the actual criteria for being judged legally insane are. It also concedes that the audience doesn't know that Gotham uses the same test the real-world US legal system does (which varies from state to state, but they're all more or less based on the Model Penal Code), so maybe under Gotham's definition voluntarily being seen in public in green spandex is all it takes.
    • Not all the people listed are sent to Arkham. The Penguin is normally just sent to a normal prison (Blackgate Penitentiary). It was also a plot point that most of the Mooks you fight in Batman: Arkham Asylum had to be sent to the Asylum after a "mysterious" fire.
    • The general consensus is that the insanity defense is almost guaranteed to work in the Gotham court system regardless of how much sense it makes legally, but since it means going to Arkham, you'd need to be crazy to try it. In Arkham Asylum: Living Hell, Warren White, an embezzler who stole millions of dollars and unfamiliar with Gotham, made this mistake and found himself in Arkham instead of the cushy rehab center he expected to be sent to. Things didn't go well for him; Killer Croc attacked him, slashing his throat and giving him "gills". Then an encounter with Jane Doe in Mr. Freeze's specialized cell left him without hair, ears, nose, and lips. Then White filed his teeth to points and took the name "Great White Shark". Essentially, while he might not have been crazy before his insanity defense worked, he certainly was after it.
      • In The Batman Strikes Black Mask's lawyers used the same defense with the same results, ie Black Mask being sent to Arkham. Bear in mind this is set in The Batman universe where the inmates are less cordial, less restrained, and Arkham is less about reform than containment. The last panel points out how bad of a move this was by having Bruce not concerned in the slightest while showing Black Mask facing the bulk of Batman's rogue's gallery, with the kindest interpretation being they're going to break him. Oops.
    • Also, not everyone who gets sent to Arkham is sent there due to being considered insane. Mr. Freeze is (usually) sane, but he's still there because it's the only imprisonment facility with the technology to keep a cell refrigerated enough for him to survive in it. Granted, this probably counts as an abuse of his human rights because it keeps him from interacting with sane people, but he hates everyone anyway, so he won't complain.
    • Depending on the Writer, Poison Ivy may be a valid case. Neil Gaiman's origin story strongly implied that Jason Woodrue raped and experimented on her to the point that her original identity is barely a memory, and her current personality is either a trapped plant spirit or so warped that it believes such, making her thought processes so alien that the only one who really "gets" her is Harley Quinn.
    • Woodrue himself, as the Floronic Man, eventually gets remanded to Arkham following a psychotic break in the pages of Swamp Thing, where he reaches the plant consciousness of earth and attempts to kill all animal life without realizing doing so would doom the plants he thought he championed. He has since become more a case of Blue-and-Orange Morality, drifting further away from anything resembling rational thought.
    • Harley herself almost qualifies, as she's something of a textbook case of Stockholm Syndrome made worse by being sent back to Arkham right along with Joker, her abuser. Her New 52 origin story retconned this to some form of permanent psychosis from brain damage or drugging, with Harley eventually rejecting Joker outright. In this version of events, she's not legally insane and sent to Belle Reve Penitentiary instead of Arkham.
    • Firefly would legitimately qualify as a Pyromaniac if he didn't also enjoy killing people. Pyromaniacs can't stop themselves from setting fires, even deadly ones, but Firefly's so openly happy with the consequences even then that the legal system would probably come to the conclusion that he understands morality.
    • Clayface III (Preston Payne) was also a legitimate case. Due to his Touch of Death and Power Incontinence, his mind snapped from the guilt of killing innocent people, to the point where he believed his cell was an apartment he shared with his wife, unbeknownst to him a mannequin. While Payne knows what he is doing is wrong, he believes he experiences severe pain if he doesn't periodically kill someone.
    • Minor villain Humpty-Dumpty is also legitimately insane, and honestly thinks dismembering people and reassembling them (poorly) is best for all involved, with no malice involved. While an extreme case, he's not malevolent in any way... at least not before meeting the general population of Arkham.
    • An additional legitimate case is the Ventriloquist, who truly believes that his Demonic Dummy Scarface is alive and forcing him to commit crimes under threat of violence, with the delusion being so strong that even destroying the puppet fails to free him, as Wesker will instinctively create a new body for his "boss" at soonest opportunity when it happens. The exact nature of Scarface itself is purposely uncertain, but whatever the case, Wesker's certainty that he has no agency in his crimes and is only committing them under duress is easily provable, and he could probably get a successful plea off the simple fact that he compulsively self-harms as result of Scarface, doing things like shooting his own hand or purposefully beating himself with the puppet when Scarface supposedly gets mad at him.
    • It doesn't help that Gotham's psychiatrists tend to get outed as villains themselves (Scarecrow, Hugo Strange, Dr. Hurt, Harley Quinn, the various Doctors Arkham) or are shown to be grossly incompetent or negligent. When a steady stream of new inmates ensures new test subjects or funding from bribes, it's easy to see why they'd play fast and loose with the legal definition of insanity. This situation goes all the way back to the place's founding; the man who built the asylum, Amadeus Arkham, went mad after one of his patients murdered his wife and daughter (and he promptly murdered the patient in revenge), spending the remainder of his life after locked up in his own Bedlam House. Note also that the land Arkham is built on — possibly including Gotham itself — is all but explicitly stated to be cursed, haunted, or some other form of Eldritch Location.
    • Another thing worthy of noting is that it's frequently implied Gotham's legal system is overloaded at best, openly corrupt at worst. Given that Arkham's infamous for its escapes and the horrific nature of its inmates, part of the high rate of legally sane people incarcerated there is because they fully intend on leaving soon, and partly because many of Gotham's lawyers and judges seem hellbent on keeping all of Gotham's worst right in one place where they can at least be kept track of if nothing else. With Blackgate's introduction, it also helped separate the big-name villains from their Cannon Fodder henchmen.
    • The conclusion of Identity Crisis may be an indicator of how easily anyone can be committed to Arkham without any legal proceedings. After discovering his Ex-wife, Jean Loring, killed Sue Dibny, Ray Palmer simply dumps her in Arkham. The crime was committed nowhere near Gotham, she clearly understood it was illegal considering the steps she took to cover it up (she is a criminal lawyer, after all), and since they're divorced Ray had no legal standing to commit her.
    • The Batman comic's abuse of this is deconstructed with one of his rogues, Lock-Up, a former security guard who went mad and became a Vigilante Man partly in response to his growing rage over seeing supervillains in Gotham regularly get remanded to Arkham only to escape.
  • Diabolik: Attempted in Diabolik's trial, though only out of desperation: Diabolik had not named an attorney nor collaborated with the one assigned to him, so the lawyer, not having anything to work with, tried that when he noticed his charge seemed to have a blinking tic. It failed and Diabolik was sentenced to death, though he escaped just in time... But years later this and other irregularities at the trial were used by anti-death penalty activists as evidence that Diabolik had been subjected to a Kangaroo Court and that he should be retried, convicted properly, and sentenced to life in prison (as in the meantime more than enough evidence of his many crimes has emerged).
  • Green Lantern:
    • When Hal Jordan fought an opponent code-named the Aerialist, it became obvious that the Aerialist was under a severe delusion making him believe that his criminal actions were entirely legal and correct. Hal referenced the M'Naghten rules when wrapping up the case, his opinion being that the Aerialist would qualify for an insanity defense.
    • Black Hand's current backstory strongly implies he's legitimately insane, compulsively wallowing in death as an erotic experience, often hearing voices compelling him to kill. Mind, Black Hand hears voices because someone's legitimately talking to him...
  • MAD: A Lighter Side cartoon about trials had the judge mock the defendant for wasting his insanity plea on a parking ticket.
  • Spider-Man:
    • Villain Sin Eater (famous for killing Spidey's long-time ally Jean DeWolff) is a notable example of this trope being done correctly; Sin Eater actually was legitimately mentally ill (a drug he tested during his SHIELD days left him with psychotic urges that manifested as an alternate personality that urged him to kill) and committed his murders because of this. His insanity defense led to him getting the psychotherapy he needed, and when we next see him, he's slowly recovering and guilt-ridden from the crimes he committed. Either way, he isn't a threat to anyone else now, as his final fight with Spider-Man was so brutal, it left Sin Eater a stuttering wreck who needs help getting around.
    • After he was cured Morbius stood trial for his crimes committed during his time as a living vampire. His attorney Jennifer Walters successfully argued that he was not responsible for his actions because his condition literally drove him insane, providing proof in the form of a rabbit that turned violent and killed another rabbit after being injected with the same serum. The jury found him not guilty by reason of insanity, avoiding the death penalty. Nevertheless, Morbius still wallows in guilt for what he has done and tries to atone in several ways.
    • Serial killer Cletus Kasady was originally sentenced to Ryker's Island, but after becoming Carnage, he started being shipped to the Ravencroft Institute instead, as acquiring superpowers exacerbated his nihilistic belief system to psychotic levels. He does not believe that the horrible things that he does are wrong, because he sees law and order and existence itself as pointless, and it's everyone else who is crazy and stupid for not seeing the truth; that we should all do whatever we want because nothing matters and there's no such thing as morality, and to think otherwise is unnatural and delusional. As Ravencroft became less and less equipped to handle him, he started being locked away in specialized facilities (like the Raft) with other villains, crazy or not.
    • There was a period where War Machine had an advanced interface that displayed how many people his foes had killed, allowing him to decide whether or not it was okay for him to use lethal force against said bad guys. When he faced Norman Osborn, Osborn pointed out that War Machine couldn't kill him since all of the Goblin's murders were committed while either being certifiably insane as the Goblin (such as Gwen Stacy and Terri Kidder) or while in the service of his country (Queen Veranke). War Machine's response was to say "Interesting theory" and then blast him with a rocket. For the record, Osborn was lying- he attempted, arranged, and committed plenty of murders even after being (temporarily) "cured" of the Goblin personality, and the first time he was thrown in jail it was actually because he was murdering young women for kicks as Norman Osborn, not as the Goblin; Rhodey (hopefully) blasted him because he knew this.

    Comic Strips 
  • Calvin and Hobbes: In one Christmas story arc, Hobbes acts as Calvin's lawyer in his letter to Santa. Needless to say, the only defense Hobbes offers is to prove Calvin is insane, simply because he considers it impossible to argue Calvin was innocent.
  • In one old The Wizard of Id strip, a lawyer pleads insanity for his client, even though the crime was stealing a pie. The reason? Would a sane man steal a rhubarb pie?

    Fan Works 
  • Create Your Own Fate: After being charged with the (semi-justified) beating-bloody of a group of teenagers and the (unjustified) assault on a pair of Bajoran Militia officers while being taken into custody, Sheri Walford, through her attorney, enters a plea of "not guilty due to traumatic mental impairment" (essentially "I was not in full control of my actions because I was having a PTSD-induced flashback at the time"). The Bajoran court system seems to have some experience with these given the Occupation, as the prosecution asks for a reduction of all charges to misdemeanor and a summary judgment. The judge interviews Sheri, and upon finding she's not even completely sure how many attackers there were, seemingly confusing the event for something that happened while she was a Child Soldier, concurs, convicting her of misdemeanor assault and sentencing her to community service and mandatory psychiatric counseling.
  • Tales of the Canterlot Deportation Agency: Luna Vs. The Law Machine: "Cleaning Up The Town": It's how criminals choose to get moved into a Cardboard Prison / asylum to be freed at need by the evil villain running the city.

    Films — Animated 
  • In Aladdin, when Princess Jasmine disguised as a commoner accidentally steals an apple, Aladdin saves her from getting her hand chopped off by claiming she's his sister and insane. Jasmine quickly plays along.

    Films — Live-Action 
  • 22 July: Breivik's attorney advises him to plead insanity, telling him it could keep him out of prison. Breivik initially goes along with the idea purely because he finds it funny since people would inevitably be upset at the prospect of him avoiding jail entirely. Breivik backtracks on this only because he realizes that, if he's declared insane, no one would take him or his ideals seriously.
  • In Anatomy of a Murder, the defense's entire argument rests entirely on the "irresistible impulse" insanity defense.
  • In Batman Begins, Dr. Johnathan Crane (aka The Scarecrow) helps mob boss Carmine Falcone by testifying to the insanity of Falcone's thugs and having them put in Arkham Asylum to avoid jail time. But while there, he does twisted experiments on them to drive them to insanity.
  • Aversion in Nuts, where Barbra Streisand demands they declare her sane. The film notes (accurately) that if you are declared insane, you can be kept locked up for life, even for a crime that would only entail a few years in prison.
  • One Flew Over the Cuckoo's Nest deconstructs the trope; playing insane got McMurphy transferred into a mental institution, which he knows about and thinks is better than prison. He is sorely mistaken: the head nurse is sociopathic and psychologically abusive, he has a near meltdown when he learns that, unlike prison where he has a set release date, the mental institution can keep him indefinitely until they deem him sane, and it ends with him lobotomized and then mercy killed by an inmate after he snaps and attacks Nurse Ratched after she inadvertently causes another inmate to commit suicide and shows no remorse over it.
  • Training Day: Mentioned by one of the three wise men when he recaps to Alonzo how an off-screen criminal recently got off this way by pulling a stunt in court that made him seem mentally unsound.
  • Judge Dredd (movie only)
    Rico: I remember you. Testified before the Council that I was insane, right?
    Ilsa: And therefore innocent. I was trying to save your life.
    Rico: What you did was insult me, 'cause I knew exactly what I was doing. Then and now.
  • M: The killer gives a The Reason You Suck speech to the criminals who conduct his Kangaroo Court trial, saying that he's driven to kill because he has serious mental problems, while they have no excuse for committing their various crimes. Ultimately we don't hear the killer's real court defense or the real court's ruling.
  • Depending on which version you watch, William Friedkin's Rampage is either the opposite, or agrees.
  • Inception inverts this; Mal had herself declared sane by three different psychiatrists, so as to prevent Cobb from being able to explain the nature of her madness, as part of her plan.
  • Rowdy Rathore treats this as a "Get Out Of Jail Free" card without any mention of psychiatric treatment; justified in that the Big Bad has clearly bought the judge and no one in the story believes otherwise.
  • In Miss Congeniality, Grace sarcastically suggests that Cathy Morningside shoot for an insanity plea after rigging the Miss United States crown to blow up and kill the contest winner, purely out of spite for being fired from running the pageant, and then having the audacity to claim the whole thing was a plan to make the world "a more beautiful place".
  • Side Effects has suicidal Emily take various antidepressants before taking a new experimental drug called Ablixa, which appears to be working until she murders her husband while sleepwalking. At the trial, her current psychiatrist Dr. Banks argues that the drug is to blame, and the defense ends up offering an insanity plea. The trope is slightly subverted in that it's specifically mentioned how low the percentage of success for this type of defense is. Emily is only acquitted by reason of insanity in a plea deal since the prosecutor realizes that he can't win here, and she must remain in a hospital over a set period. Subverted in that she knew precisely what she was doing and planned the whole thing with her former psychiatrist Dr. Sieber in order to kill her husband and cash in on the pharmaceutical company's stock plunge. At the end, Dr. Banks character figures it out and puts her back into the mental hospital.
  • In the 1962 film version of Chushigura, Lord Asano is allowed the chance to claim that he was mentally deranged when he attacked Lord Kira, and thus not responsible for his actions. Asano refuses to take this easy way out, as it would be dishonorable to lie to save himself.
  • In Vera Drake, Susan's doctor coaches her to lie to her psychiatrist and say she has a family history of mental illness and will kill herself if she must take the pregnancy to term. Justified since she was raped and this is the only way she can obtain an abortion legally, and even then, the price is steep.
  • Primal Fear: After the trial starts, an accused murderer's attorney realizes that his client has Multiple Personality Disorder (i.e. split personality) and that one of the personalities committed the crime. He tries to change his plea from "Not Guilty" to an Insanity Defense. After a dramatic courtroom scene, the judge agrees and says she'll send the client to a mental hospital for treatment. At the end, it's revealed that the client was faking insanity to get away with the murder. The killer, for all his cunning, seems not to be aware of the "institutionalization is usually longer than prison" trope, though he might just have been trying to avoid the death penalty (lethal injection was mentioned earlier in the film).
  • In A Time to Kill, the defense lawyer protagonist argued that the rape of his client's daughter combined with the likelihood of the culprits getting off lightly drove the defendant temporarily insane, causing him to kill both rapists with an assault rifle. This plea is somewhat undermined when the prosecution points out that the psychiatrist he brings in to support his argument was convicted of statutory rape and pressures the defendant into angrily declaring that he still thinks the rapists deserved to die, but in the end, he's found not guilty. They didn't find him "not guilty by reason of insanity", just "not guilty", and thus he couldn't be committed without evidence that he really was mentally ill — which the prosecution had not accepted. The insanity defense is not what gets him off at the end, anyway, but the jury sympathizing with him via his lawyer's speech. This is arguing for jury nullification, though, since he never mentions the insanity defense in his closing argument, and no judge would permit it. Some of this is down to the film being a slightly Compressed Adaptation of the book that cuts out a lot of the nuance that made the story at least somewhat plausible (see under "Literature").
  • Batman v Superman: Dawn of Justice. Lex Luthor (who certainly is suffering from a mental or personality disorder) claims he's too crazy to stand trial after being thrown into prison. His smugness slips a fraction when Batman agrees... and informs Luthor that he's being shipped to Arkham Asylum, where Batman has some friends who'll make Luthor's life unpleasant. Of course, Luthor is definitely unhinged after witnessing a god-eating abomination heading straight for Earth.
  • Appears in 15 Minutes, in which the murderers exploit If It Bleeds, It Leads and plan to plead this, get sent to an asylum, be suddenly "cured", and make a killing by selling the story afterwards. Their mistake is explaining this on tape since a key component of an insanity defense is that you didn’t know the criminal action was wrong at the time you committed it.
  • Cop: At the end, the killer, after failing to kill Hopkins and out of bullets, throws his arms up and taunts Hopkins that he'll just go for the insanity plea. Hopkins executes him on the spot right before the credits roll.
  • In the film Final Analysis, a woman is tried for murdering her abusive husband. Her defense is that she did so while in a psychotic state brought on by alcohol consumption (she normally does not drink, but took a sip of cold medicine that night). She's found not guilty by reason of temporary insanity and sent to a mental hospital where she anticipates being released in a few months. Until her psychiatrist/lover learns that she's been faking it the entire time. At the hearing where it's to be determined if she can be released, he provokes her into a screaming fit, leading her to be permanently institutionalized.
  • Dream Lover: A Femme Fatale gets her husband committed to an insane asylum to steal his fortune. He lures her to his sanitarium and strangles her to death while explaining that the courts will rule him not guilty by reason of insanity for her murder. He claims, "In a year, I'll be sane again, and they'll have to let me out."

  • Primal Fear, as with the Film of the Book above, has an accused murderer's attorney discover his client has multiple personalities, and that one of them is the actual killer. The judge dismisses the case and orders him to be committed to a mental institution until he's cured. In the sequels, he manages to fool his doctors into thinking he's cured and get out — where he kills again.
  • Deconstructed (at least in the 'Declared insane= gets off basically scott-free' aspect) in One Flew Over the Cuckoo's Nest. Randle Patrick McMurphy tries to invoke this and pretends to be insane in order to use this defense because he's too lazy to serve out a rather light sentence on a work farm. When he gets to the asylum, he quickly realizes that the asylum is way worse than the prison would be, patients don't have set sentences after which they go free and must stay until declared well- which, considering he's pissed off the evil Nurse Ratched (the reason the place is so awful) is probably not going to happen for him.
  • Comes up in The Krytos Trap. Tycho Celchu is accused of murder, and there's a lot of evidence that he did it. A few years ago, he'd been kidnapped by Ysanne Isard, Manchurian Agent maker extraordinaire. People who think he did it are divided between thinking that he'd been brainwashed and thinking that he was a garden-variety traitor; there's evidence for both. His lawyer tells Tycho that if the Tribunal decides he was brainwashed, he'll be declared not guilty by reason of diminished sapience and put into a hospital to be treated, and released when he's cured. That sounds nightmarish to Tycho, but the Tribunal's nightmare is that he'll only be there for a week or two before treatment ends and he'll be released. This would make the justice system seem impotent; the nonhuman public thinks he's a traitor and isn't very sure about their government as it is. The human public is starting to believe that he's actually innocent, since there's proof of that too, and is being offered up to placate the nonhumans. It's sticky. In the end, he's declared completely innocent when the victim turns up alive.
  • In Red Dragon and The Silence of the Lambs, Dr. Hannibal Lecter was committed to a mental hospital after being convicted of killing and cannibalizing several people and the attempted murder of an FBI agent. The hospital's director Dr. Chilton describes him as a "pure psychopath". Lecter's case wouldn't fit the legal definition of insanity since, based on the discussions he had with Starling and others, it's clear that he was in full possession of his (admittedly impressive) mental faculties and capable of understanding the consequences of what he was doing. In Hannibal, Starling explains that Lecter did not actually plead insanity, but rather that it was the jury that found him insane, the reasoning of the courts being that Lecter was such a respectable, successful, and intelligent individual that the only possible explanation for his crimes was that he was stark raving mad. In the Film of the Book, the headline reads "Lecter Given Nine Life Sentences" or something like that, but he is still put in a mental institution for treatment, which can often occur even when the defendant is found guilty but still has a disorder. Many prisons now have their own psychiatric wards, in fact.
  • Older Than Steam: In Don Quixote, Cervantes explains this trope is the reason for why Don Quixote is never killed or sent to jail (though he is often beaten) by the poor Innocent Bystander of the day. Note that it's another character who invokes it, because Don Quixote himself cannot, since he obviously is not mad — those jealous wizards transmuted the giants into windmills! It may be the Ur-Example.
    "...The landlord shouted to them to leave him alone, for he had already told them that he was mad, and as a madman he would not be accountable even if he killed them all..."
  • Parodied in Soul Music, when a murderer who has already been executed tries to convince Death that "the balance of my mind was disturbed". His logic? "I really wanted to kill him. You can't tell me that's a balanced state of mind."
  • What Benjamin and his lawyer try to pull in Hollow Places. While it's obvious that a serial killer who murders women by drying them out in glass boxes and has a thing for dead bodies isn't entirely sane, it's made clear he knew exactly what he was doing.
  • In the third book of The Hunger Games, Katniss is declared insane after she killed President Coin for sending Prim and other children to their deaths.
  • In The Adventures of Tom Sawyer, Muff Potter's lawyer said to the jury he wanted to introduce this defense on account of his client's drunkenness before making Tom and Huck testify.
  • In After the Golden Age, the supervillain Simon Sito, also known as The Destructor, uses the insanity defense at his trial. The protagonist initially believes it to be a ploy and works with the prosecution to prove that Sito is sane; later in the book, however, she contemplates how Sito has never shown any interest in money, power, or sex, seeming to be solely obsessed with destruction for its own sake, and starts to consider the possibility that he really is insane.
  • Jane Boleyn tries this in The Boleyn Inheritance to save her from being executed. It doesn't work because the king just changes the law so anyone can be executed, even if they are mad.
  • Death Shall Overcome: After a minor character tries to open fire on a NAACP fundraiser, it's suggested that he should plead insanity to beat the rap. "Loudmouth racist" wouldn't qualify for that defense, but on the other hand, no lawyer was involved in that plan — the character's latest Trophy Wife and his estranged son came up with this on their own, as much to get their hands on his money as to keep him out of jail. note 
  • Discussed in I Heard That Song Before. As the prosecution closes in, Peter intends to plead he's not guilty of murdering Susan because it occurred while he was sleepwalking and therefore he wasn't in control of his actions. His lawyers state that the jury will probably just see this as a new spin on the insanity defense and that it probably won't work; they tell Kay that while this defense is applicable in Canada, in the United States sleepwalking isn't a valid defense in a murder trial, and there are two people currently serving life sentences in the US for committing murder while sleepwalking.
  • The Zombie Survival Guide: In one account of a zombie incident that took place in early 20th Century Africa, a Native Guide named Simon is accused of the murder of a white man called Schmidt. Simon's lawyer states that Simon's people believe in an illness that causes corpses to rise and attack the living, and his decapitation of Schmidt and burning of his body was motivated by self-defence as he believed Schmidt had contracted the illness. He then quickly adds that he himself doesn't believe in this illness and only mentions it to the court because he believes it qualifies Simon as insane. Unfortunately the court rules that only whites qualify for the insanity defence and sentences Simon to death.
  • Comes up in a few places in the works of G. K. Chesterton.
    • In Four Faultless Felons, a young doctor comes to suspect that the father of the girl he loves might be a murderer, and knows there is a detective looking for him. He hastily whips up an official-sounding diagnosis to justify comitting the father to a lunatic asylum before he can be arrested.
    • One of the villains of The Poet and the Lunatics is a corrupt psychiatrist who runs an organized crime ring out of his hospital. Having certified his minions as lunatics, he simply lets them "escape" when he has a job for them, and if caught they are simply sent back to him instead of being jailed or executed.
  • A Time to Kill handles this slightly better than its movie counterpart, with the lawyer devoting more time to demonstrating the defendant's mental state and actually making a proper closing statement (the lawyer's statement in the film — which is wildly inappropriate for a closing statement — is drawn from part of the jury discussion in the book). While the result is still pretty obviously jury nullification, it comes with just enough plausible deniability that a court would probably feel compelled to accept the verdict even if they suspected jury nullification was in play.

    Live-Action TV 
  • In Apple Tree Yard, Mark pleads this after being charged with George's murder. It ultimately succeeds in his sentence being reduced from murder to manslaughter due to diminished responsibility. Whilst not confirmed, it's implied that at the very least he's got some pretty abnormal ways of thinking and behaving, including taking Yvonne literally when she jokingly told him she wanted him to kill George for raping her (she just wanted him to get George to stay away from her).
  • The Made-for-TV Movie The Burning Bed is a good example of a well-supported "temporary insanity" plea. The film is Based on a True Story, and in Real Life, Francine Hughes was acquitted of killing her husband by setting fire to his bed as he slept, saying she only did it because he was extremely abusive to her and she believed he would eventually have killed her even if she left him.
  • Judge John Deed: James Brooklands tries this, backed up by an army of psychiatrists, to avoid standing trial for killing a family by dangerous driving. John is not fooled, and cleverly breaks his cover.
    John: Well, it seems eminently sensible, that to protect the public, perhaps I should commit Mr Brooklands to Broadmoor. (Said dramatically, looking Brooklands in the eyes)
    Brooklands: (horrified, suddenly breaking out of his catatonic state) No! No!! You can't.
    (The jurors turn their heads to look at him)
    Defence barrister: My Lord, that's not a proper response!
    John: (cheerfully) Yes, you're quite right, it isn't. Your client doesn't seem to think so either.
  • Law & Order:
    • The show frequently addresses this, as many defendants plead 'not guilty by reason of mental disease or defect' (which is how they phrase it) and court/prosecution-appointed psychiatrists are often featured for this reason; rarely are the defendants actually found to be legally incompetent to the degree that is required by law for such a plea to be accepted without trial, and even fewer actually have this plea accepted by a jury. The Catch-22 bind is often addressed in episodes where the situation is inverted; the defendant clearly is mentally incompetent, but insists they are sane.
    • The episode Pro SE has the unusual spectacle of a guy using an insanity defense while defending himself. His claim is that he was insane when he committed the crimes, but now is normal thanks to medication, so it's not as ludicrous as it first seems. He is a paranoid schizophrenic, leading to him becoming homeless and murdering people due to his delusions. Before, however, he earned a law degree and is practicing (while defending himself) for the first time. The prosecution tries to make the claim that he is sane as long as he takes his medication, and the decision to stop doing so is sufficient to make him guilty.
    • One inversion occurred when an obviously insane defendant who murdered three people refused to allow his attorney to plead insanity, even though he was obviously guilty and eligible for the death penalty if convicted.
    • Another subversion was what appeared to be an extremely deranged person pleading it, appearing to be actually insane (voices in his head, erratic behavior, violent reaction to loud noises, etc.) only for the court psychiatrist to see that his symptoms were too good, figuring out that he was only pretending to be insane.
    • Then there was an interesting case. The defendant actually was hearing voices in his head. However, it wasn't insanity causing the voices, it was a brain tumor, and the defendant had such a short life expectancy that putting him on trial would be rather pointless. His doctor was charged with criminal incompetence, with the promise that once the defendant died, the doctor would also be charged with homicide (since the tumor was operable when the doctor discovered it).note 
    • A similar case in the below mentioned SVU had a spree killer be sentenced to a psychiatric facility until he is deemed fit to stand trial (which will likely never occur) after it is discovered that his erratic behavior and murders were caused by his mind being destroyed by a now terminal case of Syphilis, which an insurance company had detected during an exam, but failed to inform him of. The insurance company also failed to inform the Center for Disease Control, which Cabot uses to justify bringing charges against them.
    • Inverted in one episode the teenage defendant has bipolar disorder but his grandfather refuses to let him plead insanity since he doesn't want the fact that he also has bipolar disorder coming to light. This leads to the unusual situation where the prosecution is pushing for a psychiatric evaluation and possible verdict of insanity rather than the defense.
    • While it's rare, there are a handful of cases across the franchise where a defense of this type turns out to be valid. In most cases where this happens, there will turn out to be some kind of corollary or underlying crime which then becomes the focus of the episode.
    • Some episodes in both the mothership and the spin-offs invoke the separate, though related, standard of being unable to stand trial. This is in effect a step above the insanity defense, basically saying the defendant is in such bad mental condition that even holding a trial would be unfair. In this scenario, the defendant is held in a psychiatric facility until such a time as they're even able to comprehend the proceedings and assist in their own defense. One episode has Olivet invoking both concepts at once, as she explains that not only is their defendant currently incapable of standing trial, but also, if she ever does reach a point where she could be brought to trial, she'd have a slam-dunk case for an insanity defense.
  • Law & Order: Special Victims Unit: Sexsomnia, watching too much TV (Oz), borderline mental retardation (as noted below), schizophrenia, sexual addiction, even a brain tumor have all been successfully proffered as rape defenses, and in nearly all of these cases, the defense is valid. As with the mothership, defense lawyers still habitually trot out the defense as a last resort when the client is caught red-handed, only to get their asses handed to them when a last-minute fact torpedoes their whole case.
    • It's used to chilling effect in an episode where a mentally disabled man rapes an old woman (causing her to have a heart attack) because her position greatly resembles a porn flick he was shown, and he didn't understand the nature or consequences of what he was doing, thus he is acquitted. The prosecutor is infuriated that he 'got off easy' by not being put in prison — but then it cuts to the man being put into a mental institution by one of the detectives, still unsure of what's going on and seeing the various mentally disturbed people talking to themselves or wandering around in an unpleasant gray facility. The final shot is of the horror on the man's face.
    • Subverted in episodes of both shows when insane defendants refused to plead insanity for different reasons, forcing the prosecutors to come up with a roundabout way to introduce the evidence of their insanity or compel them to reveal it by goading them into a courtroom outburst of some sort.
    • In one episode a psychiatrist murders a child who had murdered the doctor's son and then tricked him (the victim's father) into pushing for leniency, which it's now too late to retract. The psychiatrist is acquitted on an insanity defense but later admits that it actually was planned and not a fit of grief/rage as had been claimed. Since he's already been acquitted, there's nothing they can do about it.
    • A rare case where it's actually valid involves a schizophrenic man who abducts a child that he mistakes for his own estranged son and kills two people who try to stop him, believing they're trying to hurt his "son". The detectives determine that he really didn't understand what he was doing, and he's sent to a psychiatric hospital rather than prison. They later find out that the care facility he was living in illegally denied him his medication (which he was doing very well on before it was taken away) so that no one would believe him about witnessing another patient dying due to neglect; this makes the facility's owners liable for the kidnapping and resultant deaths.
  • In one episode of Law & Order: Criminal Intent, the user of the insanity defense is a police psychologist. The detectives eventually prove that he'd killed a man in a misguided and misinformed attempt to impress a woman he was in love with, with the Insanity Defense as a contingency plan.
  • Parodied in Community. The Insanity Defense is used by Jeff to keep Britta from being expelled from Greendale, arguing that she deliberately sabotaged herself by cheating on a test in order to fail and get kicked out, thus validating her own low sense of self-worth. He then goes on to argue that since everyone at Greendale is crazy in one sense or another, it would be an act of gross hypocrisy to kick her out based on this. It actually works.
  • Used in Bones. Zach Addy was deemed insane in an off-screen trial, and went to a mental institution. Eventually, the audience finds out that he didn't actually commit the crime he was accused of, but believes that he may have committed a lesser crime and refuses to confess because then he could be re-tried and might go to jail.
  • One episode of Criminal Minds has Hotch tell the killer himself "You were sick. You didn't know what you were doing", because the man is freaking out while in custody, having just realized that he is actually guilty of the crimes they're accusing him of. The last shot of the episode is the killer in a mental institution. There are a number of other episodes where you don't see the killer in an institution, but it's pretty obvious that the defense applies.
  • The Firm on The Practice would cut-and-paste the Insanity Defense around any sympathetic defendant who performed a Vigilante Execution to give the jury an excuse to acquit their client, since arguing an eye for an eye would be considered jury nullification. The chances of a jury buying it were generally low. The episode "Committed" showed the aftermath of one of these: a serial killer who used a successful insanity defense some years ago hires Lindsey to help him get declared sane and released from the institution he is now in.
  • Attempted by Serial Killer Nate Haskell in CSI, who argues that a combination of childhood abuse and possessing the MAOA gene (which has been linked to an increased propensity for violence) turned him into a sadistic psychopath. His Arch-Enemy Ray Langston shoots him down in court by announcing that he also had an abusive childhood and also possesses the gene, but he became a doctor rather than a murderer, and Haskell later admits in private that he made a conscious decision in his youth to blame everything on the two in the event he was caught. There's a lot of Fridge Logic involved in the case — it is strongly implied that if Haskell were found insane, he would actually be let out of custody, despite his entire defense boiling down to "I'm a sadistic, murdering psychopath. And I'll probably do it again." This is a common mistake in the depictions.
  • It's Always Sunny in Philadelphia: Mac and Charlie believe that “Psycho Pete,” the former leader of their “Freight Train gang”, killed and ate his parents for dinner and was institutionalized. This turns out to be something they made up entirely. He was actually there for extreme social anxiety, which he still suffers from.
  • JAG: In "Act of Terror", a Marine guard is charged with murder after he shot a terrorist suspect during a prisoner transfer, on live TV. Harm, as defense counsel, begins to explore the option of an insanity defense, but he’s taken off the case by the defendant, who’s hired a different attorney.
  • Cracked (2013): Given that the show deals exclusively with cases involving The Mentally Ill in some capacity, many of its perpetrators would be judged not fit to stand trial, not guilty by reason of insanity, or to have suffered from diminished capacity. The episode "No Traveller Returns" is dedicated to establishing whether cannibal murderer Mandar Kush, who has spent eleven years in an institution, can be released into society. The answer is yes.
  • Used in an episode of Psych. Interestingly, the episode begins after the defense has been used and the sentence passed. Lassiter becomes enraged by the verdict and thinks the defendant was faking it, so he sends Shawn to investigate. The defendant was actually insane, but wasn't actually the murderer.
  • Accused: Discussed in "Stephen's Story". Stephen's attorney wants him to get a psychiatric examination so they can prove he was insane at the time of his crime (he's clearly a schizophrenic). Stephen refuses, though, denying he's mentally ill and claiming what happened was justified to defend himself and his family. This doesn't work, and he gets convicted of attempted murder.
  • Played with in the second (and final) episode of Made in Jersey. Martina defends a severely schizophrenic young woman who took an insanity plea for murder but now wants a retrial so she can go home. She's innocent and Martina successfully gets her acquitted.
  • Manhunt: Unabomber: Kaczynski categorically rejects using one, as he's terrified of being put in a mental institution (no doubt due to his highly abusive experience at the hands of a psychiatry professor who used him in a psychological experiment) and since it would threaten the credibility of his message. He's enraged when his lawyer is revealed to have prepared it anyway in spite of his express wishes and tries to fire her so he can represent himself. The judge however refuses until he's ordered a psychiatric evaluation, and warns that if they decide Kaczynski is a danger to himself or others, they will begin treatment immediately. Put in a bind, Kaczynski pleads guilty and gets life without parole, but avoids a mental institution.
  • One episode of My Family offers a rare (and extremely incompetent) example of the "diminished capacity" defence. After Susan impulsively shoplifts a pair of sunglasses and is put on trial for shoplifting, Ben appoints himself as her lawyer and, against her wishes, proceeds to aggressively and chauvinistically pursue a verdict of "diminished responsibility on the grounds of the menopause". The female judge eventually lets Susan go, not because Ben's defence actually worked, but because she's so disgusted by his attitude that she pities Susan for having to put up with him.
  • Accused (2023): "Danny's Story" features this. The titular character, faced with an attempted murder charge, refuses to let his lawyer argue insanity, insisting that his stepmother really murdered his mother and he stabbed her to protect the rest of his family. Everyone else though believes he's mentally ill, and he finally acquiesces. It apparently worked, with Danny sent to a mental institution rather than prison. However, he now can't get out either, and his stepmother really did do what he claimed, having now murdered his father and begun to poison his brother as well.
  • The Confessions of Frannie Langton: Frannie's barrister proposes using her experience of enslavement in Jamaica by saying this unhinged her mind when she's charged with a double murder. Frannie firmly rejects this angrily. Later though he uses a different variety, claiming she might have committed both murders in a state like sleepwalking but wasn't really aware of her acts. Frannie herself at first fears she did this and doesn't remember it.
  • The Crowded Room: Rya prepares one with Danny's lawyer after determining he has multiple personalities. It's an uphill battle though, as at the time the disorder wasn't widely recognized to be real. The state's expert rejects it flatly ahead of the trial, plus Danny's alters won't come out with people except Rya, which causes the judge to dismiss it as ludicrous. No one has ever won with the insanity defense citing how a split personality committed the crime, it's noted, but they try anyway. It works once the jury hears from Danny.
  • In The A-Team the reason why Murdock is not sentence to jail as the other three is because he's considered crazy and is send to a mental institution where he's taken out over and over again by the rest of the team. The show is ambiguos whether Murdock is indeed crazy but funcional enough to be part of the team or just a ruse to get a out of jail free card.

  • Roy Brown's "Butcher Pete":
    Well, they put him in jail again
    They tried to give him life
    Pete beat the case, he pleaded insane
    They gave him back his same ole knife
  • The Oak Ridge Boys, "Don't Break the Code." A man finds his wife in bed with another man and kills them both.
    The jury found only insanity
    So his head stayed in prison but his body went free
  • Miracle Musical: The protagonist of "The Mind Electric" is made to testify for an unspecified crime. He tries pleading that he's a good person despite being insane. It doesn't work, leading to him being sentenced to electroshock therapy.
    Father, your honor, may I explain?
    My brain has claimed its glory over me
    I've a good heart albeit enasni
    (Condemn him to the infirmary)
  • Warren Zevon: The protagonist of "Mr Bad Example" becomes a lawyer at one point in the song and says that he advised all his clients to plead insanity. Of course, as the name suggests, Mr Bad Example is an Anti-Role Model who deliberately does the wrong thing every time and was trying to get his clients convicted after taking their money.

    Mythology and Religion 
  • In most Christian Denominations, insanity reduces or outright eliminates someone's responsibility for a sin he commits.
    • In Catholicism the three requirements for a sin to be mortal (i.e. severe enough to warrant eternal damnation) are Grave Matter, Full Knowledge, and Deliberate Consent. Since insanity takes away the second two, people who are insane are incapable of committing mortal sins.
  • In Islam, the Prophet Muhammad is recorded as saying the following with regard to this trope.
    “The Pen has been lifted from three note : from the sleeper until he awakens, from the child until he reaches puberty and from the insane person until he comes to his senses.”

    Newspaper Comics 
  • One arc of Funky Winkerbean has Lisa start working at the local public defenders' office. She's assigned a death row inmate as a client and attempts to get his sentence at least commuted by suggesting he was having a PTSD-induced blackout at the time of the murder, thereby making him not competent. This fails, she sits witness to his execution, and quits.
  • Calvin and Hobbes: Hobbs acts as Calvin's lawyer in his letter to Santa. Needless to say, the only defense Hobbes offers is to prove Calvin is insane.

  • "Tabard of Pizarro", an episode of Bold Venture, had the guest star claim that he was framed for murdering his wife, and pled insanity so as to be free to eventually claim his revenge (the villain of the story tries to frame the protagonist for murder during the course of the episode, so it seems likely the guest star is telling the truth). Unfortunately, it was many years before he was considered fit to be released. The eponymous tabard is a fake, created as physical therapy in the asylum, and used as bait to trap the villain. Oh, and the revenge thing didn't turn out so well, not being satisfying at all.
  • Old Harry's Game: Thomas Crimp tries to use pleading insanity for getting out of being tortured in Hell. Thanks to being "diagnosed" by Scumspawn using a pop-psychology book, he claims he has pretty much every possible neurological condition it's possible to have. Satan dismisses the notion and sends Thomas right back to being tortured.
  • The Trials of Marshall Hall: In "A Death at Christmas", Marshall Hall attempts to argue that his client (a Shell-Shocked Veteran) should be found not guilty by reason of insanity.

    Tabletop Games 
  • Addressed in at least two editions of Champions, thanks to Hero author Steven Long also being a practicing attorney. Game-world legal precedents have established that dressing up in a silly costume does not count as insanity, and neither does committing bizarre crimes. The villain Foxbat, who genuinely believes that he is a character in a comic book, is listed as an example of someone who could use the insanity defense.

  • At the climax of Jesus Christ Superstar, the mob is calling for Jesus's execution, taking their case to Roman Governor Pontius Pilate, the only man with the authority to order it. Pilate thinks Jesus is insane but harmless, and tries to invoke this defense against the mob, but they aren't having it. Pilate gives an impassioned defense, but when he realises that even Jesus is determined that he must die, he drops it and symbolically washes his hands of the whole thing.
  • Prima Facie: One of Tessa's clients is a veteran with PTSD. She says she'll double down on that to get him off for assault.

    Video Games 
  • Phoenix Wright: Ace Attorney: The DL-6 incident in the backstory has the defendant, Yanni Yogi, get off because his lawyer claimed insanity (specifically, that he'd suffered brain damage from oxygen deprivation after being trapped in an elevator for several hours). It's a Deconstructed Trope because said lawyer was an Amoral Attorney who pressured his client into entering an insanity plea because the lawyer didn't believe in his innocence, but was too crooked to advise a plea bargain. Yanni Yogi was both innocent and sane, but being forced to pretend to be crazy to keep up his insanity plea ruined his life and caused his fiancee to kill herself. He later murders his lawyer for what the guy had done to him.
  • In Knights of the Old Republic, if you let the lawyer appointed to you handle the trial (without telling him that you have evidence of a Sith plot) after you've broken into the Sith embassy in Manaan, then he'll try this as a last defense. It fails, and you're executed in a Nonstandard Game Over.
  • In Remember11, Keiko Inubushi avoided going to prison after murdering twelve people due to suffering from Dissociative Identity Disorder. Instead, she was sent to the SPHIA psychiatric hospital.
  • In Corpse Party, this is how Yoshikazu Yanagihori avoided going to jail for abducting four children and killing three of them. He actually was pretty insane at that point and he wasn't even the real killer, just an accomplice to the real killer, who was manipulating him, so a mental hospital was probably the best place for him. Unfortunately, security was not very good (it was 1973 Japan) and he ended up breaking out. He then broke into the school where the children were killed and hanged himself.
  • In The Caligula Effect, this turns out to have been used in a similar manner to the Ace Attorney example above, with it being used for Kouki Tadokoro after he assaulted Himari Minamide and drove her to suicide. The difference is that he really did commit the crime, but this defense (employed by Eiji, no less) still ruined his life.

  • Saturday Morning Breakfast Cereal:
    • One strip has a man defending his insanity plea with "Well, I killed a whole bunch of people. Crazy enough for ya?" Refuge in Audacity, but as explained above, not quite good enough.
    • Also inverted here. He accuses the jury of being insane.
  • Freefall:
    • Sam is a larcenous, silver-tongued alien squid. He mentions that spending more than three weeks with him is legal grounds for an individual insanity plea.
    • This is also what Blunt's defense at Mr. Kornada's trial boils down to. He argues that Mr. Kornada can't be convicted of his crimes because he was too stupid to actually understand what he was doing. Clippy was the one who actually came up with the plan, and all Kornada knew was that if he followed the directions Clippy gave him, it would somehow end up making him obscenely rich.

    Western Animation 
  • In the Futurama episode "Insane in the Mainframe", Simple Country Lawyer Hyperchicken uses the insanity defense in favor of Fry and Bender, and offers as proof the fact that "they done hired me as their lawyer." What then happens is that they're put in the mental institution, similar to what would have happened now if they weren't found "Guilty but Insane". Unfortunately for Fry, the human insane asylum is full because being poor has recently been classified as a mental illness, so he gets sent to the robot insane asylum with Bender.
  • Judy suggests using this excuse when Doug is framed for stealing Mr. Bone's trophy. Doug mentions that someone else actually tried that before but still got in trouble and had to go to the school counselor every day.
  • In Archer, Cheryl uses this tactic effectively to avoid jail time, instead being thrown into a mental hospital for ten months. She urges her friends to follow her lead in order to avoid getting arrested for trespassing.
  • Harvey Birdman, Attorney at Law:
    • Subverted in an episode. Harvey tries to use this defense to acquit his client, and it looked like the jury was going to buy it...and then a talking tapir points out that the defense can only be used in criminal cases. Harvey was defending a man in a lawsuit.
    • He used this defense earlier in "The Dabba Don" when he defended Fred Flintstone from charges of violating the RICO Act (in other words, being The Don). He successfully argued that Fred suffered from Identity Amnesia and only thought he was a mafia boss. Then it turns out that despite all clues to the contrary, Fred never was The Don. Barney Rubble was.
  • An episode of Delta State has a psychiatric patient trying to convince his therapist he is insane so the court will accept his insanity defense. He's terribly bad at it, the therapist knows beyond all reason that he's full of crap, and since the "therapist" turns out to be the rifter Maria looking for easy victims, it ends about as well for him as you would expect.
  • The Owl House: After having his ass thoroughly kicked and having no other option besides trying to talk his way out, Belos transforms back into his younger self, who Luz met when he was still going by Philip Wittebane, and tries to claim that everything he's done over the last 400 years was the result of a horrible curse claiming ownership over his mind. Nobody buys it for a single second, and Luz just stands there and watches as it starts to rain boiling water, melting Philip down while he begs for help until he's just a skull floating in a puddle of necrotic ooze, which Eda, King, and Raine proceed to stomp on until there's hardly anything left.

    Real Life 
  • Louis Riel's lawyers wanted him to plead insanity to be found not guilty of treason. People will never know if it would have worked, because Riel wanted to use his time in court as a final opportunity to make public the Métis' problems. Riel actively sought to disprove his lawyers’ insanity plea and argued that it was in fact the Canadian government that was “insane and irresponsible”. He was found guilty and hanged.
  • One of the better-known cases in recent American history was the murder of Supervisor Harvey Milk and Mayor George Moscone in San Francisco. Former Supervisor Dan White's defense team was able to convince the jury that he was in such a mental state as to be incapable of premeditation, so he ended up being convicted of voluntary manslaughter (causing riots by San Francisco gay men who saw this as an inadequate outcome motivated by homophobia). Among other things, they cited White's shift from health nut to junk food addict as evidence of his declining mental state. The references to junk food led to the coining of the term "Twinkie Defense". The term "Twinkie Defense" has now entered the language to describe a frivolously thin defence of insanity, with a common belief being that White's lawyers claimed that he should be let off because he did the killings while on a sugar high; no such argument was actually used by the defense (and Twinkies were mentioned only in passing), but people think it was.
  • A man in Alberta, Canada who beheaded and partially cannibalized a fellow passenger on a Greyhound bus in 2008 was found not criminally responsible because he was insane. He was, however, deemed a significant risk and institutionalized. A lot of people were angry that he wasn't found guilty, though others argued the verdict's meaning was misunderstood and that while the defendant might not be in an actual prison he'd spend a lot longer in a psychiatric institution — essentially spending the rest of his life in a rubber room instead of "life with chance of parole in some number of years". It turned out, however, that he was granted an absolute discharge in 2017, just 9 years later.
  • A man strangled his wife in his sleep and was released as it was decided that his sleep disorder meant that he wasn't responsible for this act. New Scientist has included a discussion of how you can show whether or not someone has a sleep disorder (after staying awake for 25 hours, a given tone woke up all the sleep-disordered positive people and none of the healthy controls).
  • John Hinckley, Jr. attempted to assassinate Ronald Reagan and is one of the few "successful" insanity defense stories. The verdict led to widespread dismay; as a result, the U.S. Congress and a number of states rewrote laws regarding the insanity defense. Idaho, Montana, and Utah have abolished the defense altogether. The dismay is ironic, as he has been in a mental institution for over 30 years, probably more time than he would have spent in prison if convicted, certainly longer than many "sane" murderers spend in prison. He was released from psychiatric care in 2016, and, as of 2021, is a singer/songwriter on YouTube.
  • The US Supreme Court ruled that people who are insane cannot be executed, on the grounds that someone who is to be executed must be capable of comprehending the gravity of their own death. However, if medication can make someone sane, they can be forced to take it so they can be executed.
  • The lawyers of Serial Killer Herbert Mullin tried this. It didn't work, as it was considered that his crimes were too well-planned to be the work of an insane person. Although he was a paranoid schizophrenic, he was found to be mentally ill but legally sane, and thus sentenced to life imprisonment. A common myth is that Mullin carried out his killings because he believed he was preventing earthquakes; while he did indeed claim this in court as part of his defence, and also argued that it worked, because there had been no earthquakes since he started killing people, his victims were people he either felt had wronged him personally (such as selling him drugs) or who annoyed him somehow (such as four teenage boys he told not to sit on the grass who were doing so), and one reason the prosecutors argued he was not insane is that once he killed a woman and her children seemingly just because they could link him to other murders. He also entertained any number of paranoid conspiracy theories and afterwards gave all kinds of bizarre excuses for the murders (he once claimed that his first victim, a homeless man, was Jonah from the Bible and that he had telepathically requested he be murdered), all of which makes it unlikely that "preventing earthquakes" was his sole motive if he really believed it at all.
  • Jared Loughner is an interesting example of just how hard it is to pull this off in real life. Prior to killing six people, he'd been forced out of college and told he couldn't come back unless he could maintain a mental health clearance proving he wasn't a danger to himself and others. The sheer incoherence of his political and philosophical ramblings got him ejected from, one of the more out-there conspiracy theory sites on the Internet, and countless witnesses on and off-line report him as having done everything from accusing his math teacher of "denying math" to spending thirty minutes in a bathroom and asking afterwards what year it was. He has since been medicated and pleaded guilty.
  • An interesting case is an ongoing thread of Jon Ronson's book The Psychopath Test, where he meets a man who pleaded insanity in the expectation that this would be a lighter sentence. Pleading insanity under those circumstances was seen by his doctors as evidence that he actually was insane — but not the kind of insane he claimed to be; it checked the item "Cunning / Manipulative" on the aforementioned Psychopath test, so he was held far longer than he would have been if he had pleaded guilty to the original offense. The book also covers a fairly chilling catch-22; if he expresses no remorse for his crime, he meets one criteria for psychopathy, but if he does express remorse, that could easily be viewed as yet another reason to check "Cunning / Manipulative". Ronson has a TED talk where he discusses this case.
  • The lawyers of the British child killer Ian Brady tried this, basically relying on circular reasoning: "My client has done something so horrible he must be insane, therefore he is insane." It didn't work initially, though he was since been transferred to Broadmoor Psychiatric Hospital — which is specifically for the criminally insane (mostly those who've killed people) and, for someone like him, basically means the most secure detention facility in the UK. He since survived a murder attempt by another inmate, which left him blind in one eye, before dying in 2017 while still incarcerated. It seems safe to say being deemed insane didn't give him any better treatment than in prison.
  • James Holmes, the perpetrator of the 2012 Aurora Colorado shootings, has apparently been called this by his defense attorney. Holmes had also dyed his hair orange and was referring to himself as "the Joker". Then again, he propped open an emergency exit before his rampage so that he could sneak into the theater past the front, and had placed a large number of complicated, connected traps in his apartment that police took several days to disable. In the end, he was found guilty by the jury but spared the death sentence.
  • This was the plea entered in the trial of Winston Moseley, murderer of Kitty Genovese. Although he did show signs of mental illness, the jury decided he did not fit the legal criteria; among other things, he said that he had deliberately counted on no one interfering with his attack, showing that he was aware of the nature of his actions. He died in prison on March 28, 2016, at the age of 81, having served 52 years.
  • Jeffrey Dahmer also tried the insanity plea unsuccessfully. He was responsible for at least 17 murders in Milwaukee between 1978 and 1991. He also experimented with cannibalism. Prevailing wisdom indicates that if Dahmer had been insane, he would have been caught much sooner, as his 13-year killing spree took a certain amount of mental faculty to hide, especially given the fact that he was able to talk himself out of trouble on more than one occasion. Ironically, he was then killed in prison by another inmate who claimed that God told him to, but also was not deemed insane.
  • In 1970 Twiggs Lyndon, the road manager of The Allman Brothers Band, got in a fight with Buffalo, New York nightclub owner Angelo Aliotta after Aliotta paid the band just $500 of a $1000 guarantee. In the middle of the fracas, Lyndon stabbed Aliotta, who died a short time later. At the trial, Lyndon's lawyer argued that being the manager of a band that heavily indulged in Sex, Drugs, and Rock & Roll had affected his sanity. As proof, they called bassist Berry Oakley to the stand, where he admitted to regularly using drugs, including right before he came to the courtroom. Lyndon was acquitted of first-degree murder, given credit for time served, and sentenced to a few months in a psychiatric hospital. Then he went back to managing the Allmans.
  • Charles Julius Guiteau attempted to use this defense after assassinating President James Garfield. Given his erratic behavior which wasn't Obfuscating Insanity (Guiteau also insisted he was only insane during the time of the murder), it was considered - before it was concluded he was insane in every sense of the word except legal. Guiteau was found guilty and hanged.
  • Mafia boss Vincent Gigante was nicknamed "the Oddfather" because he used Obfuscating Insanity so he would be unfit to stand trial. Every day, he would emerge disheveled from his home and accompanied by one of his bodyguards. His own family even pressured doctors to declare him mentally incapacitated. This "crazy" stunt eventually came back to haunt him in 1997 when mobsters from other families stated it was a ruse to shake off law enforcement. Gigante finally admitted to pulling this crazy stunt in 2003 before dying of heart disease in 2005 while behind bars.
  • English serial killer John Haigh attempted to pull this stunt off after he was arrested for the murder of at least six individuals, with his MO including disposing of the bodies in baths of acid. During interrogations, he confessed to the murders while also trying to make outlandish claims of pretending to be a vampire who drank the blood of his victims, but jurors in the ensuing trial quickly saw through the façade, reportedly due to him asking during a recess if it was easier to get out from prison or a mental institute. That, combined with the complexity of his murder and disposal process led jurors to conclude he was in fact in a perfectly sound state of mind while committing them, swiftly leading to his guilty verdict and death penalty.
  • Ted Kaczynski's lawyers initially attempted to use this in his defense to avoid the death penalty, saying that Kaczynski suffered from paranoid schizophrenia; Kaczynski refused.
  • A successful defense is MUCH rarer in real life than in fiction. It is only eligible for use in 1% of cases, and only successful 25% of the time. So 1 in 400 cases. However, 75% of successful uses are because a judge/the prosecutor AGREED the defendant was insane. So it takes roughly 1600 cases to get one successful jury verdict.

Alternative Title(s): Insanity Defence