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The Killer Was Left-Handed

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Lord Peter Wimsey: On the left, from behind downwards. That looks like another of our old friends.
Harriet Vane: The left-handed criminal.
Lord Peter Wimsey: It's surprising how often you get them in detective fiction. A sort of sinister twist running right through the character.
Busman's Honeymoon by Dorothy L. Sayers

You can determine many things about the way an injury was inflicted by studying the wound. You can determine the kind of weapon used, and what kind of motion it was making. In fiction, you can also tell the handedness of the wielder. For this to be relevant, the killer must turn out to be left-handed (which goes hand-in-hand with A Sinister Clue), or the killer's right-handedness must rule out a leftie suspect.


This can clear one person and convict another. Even though one out of every ten people is left-handed (and even though it's perfectly possible to kill someone using your non-dominant hand), being left-handed is good enough to make you the prime suspect. This can be justified, though, if only one of the suspects is left-handed. For this reason, if it's discovered early on that the killer was left-handed, you can bet that there will be at least two lefty suspects so as not to conclude the case too early.

Although it was once a common tool in detection (for example, several scholars believe that the search for Jack the Ripper was stymied by the ultimately unfounded belief that The Killer Was Left-Handed), this trope is discredited in Real Life. "Non-secretor" status may be the next generation of this trope, although it's more commonly seen in novels than in other media like TV. About ten percent of people do not have antigens in bodily fluids other than blood, so sweat, saliva, semen, etc., cannot be used for blood type comparison purposes.



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    Anime & Manga 
  • This trope is used a few times in Case Closed.
    • Most notably in Captured In Her Eyes, the fourth movie. But of all the lefties, somehow, it was the psychiatrist who did it! Yes, he's a lefty, but he trained himself to use his right hand. He slipped up though, and dialed the phone with his left.
    • The second movie, The Fourteenth Target, reverses this by having evidence that the killer was right-handed used to indicate that the left-handed person who until then was the prime suspect was not in fact the criminal.
  • The CSI: Intern at Your Own Risk Tokyopop manga has the killer be a Non-secretor.
  • Golgo 13. An actress is pretending to be a client so Duke Togo can be captured on film committing an assassination. When Togo responds to her entreaties with his trademark stoicism she has to improvise, saying among other things that the mark had injured his left hand. When looking through his sniper scope, however, Togo realises that the mark moves as if he's been using his right hand from birth, not someone who had to adapt in response to an injury.
    • In another case, Golgo has his right arm injured in a car accident and later learns that the surgeon who repaired it was the son of his next target. While he doesn't call off the assignment, he makes a point of shooting the target with his left hand. He then tracks down his client and shoots him with his right hand.
  • In one The Kindaichi Case Files story, Kindaichi proves that a victim whose handedness was unknown was left-handed based on his use of left-handed scissors, specifically designed to only function efficiently for lefties.
  • One manga Shinjuku D×D has this as one of the clues the main character used to determine someone bought a knife not for cooking: The knife he bought was designed for right-handed people yet the person themselves was left-handed.

    Comic Books 
  • Played with in The Batman's Grave #3 by Warren Ellis. Batman is investigating a left-handed man who apparently shot himself in the right temple. It turns out he did, but only because his Sinister Shrink had driven him to it ... and the exact trigger words had convinced him he needed to use his right hand.

    Film — Live Action 
  • Subverted in 22 Bullets. The police determine that the killer fired his gun with his right hand which would normally be useless information since most of the population is right-handed and a left-handed killer could have still used his right hand to fire the gun. However, the main suspect in the murder has recently sustained major injury to his right arm and thus could not hold a gun in his right hand or fire two very accurate shots with it. The police have the wrong guy.
  • This trope is used to find the mole in At Home Among Strangers.
  • It's not a murder, but the doctor in Gattaca reveals that he's always known that Vincent isn't who he says he is, by claiming that he used the wrong hand to get his urine samples.
  • Used in the Sidney Poitier movie In the Heat of the Night.
  • Man in the Attic: One of the facts Inspector Warwick says Scotland Yard has learned about Jack the Ripper is that he is left handed. On hearing this, Slade goes to some effort to conceal his handedness; taking the newspaper from Mrs Harley with both hands.
  • A variation of this occurs in David Fincher's Zodiac, where the eponymous Zodiac killer is ambidextrous, i.e. able to write with both his hands, which actually makes it a lot harder for the police to identify him based on his handwriting.

  • In The Corpse That Never Was, the killer had written things left-handed because he'd practiced writing left-handed to frame his father-in-law.
  • Death-Watch, a Dr. Gideon Fell novel by John Dickson Carr: An early clue establishes the killer was left-handed. Lampshaded / Subverted: It was part of a frame-up by the real killer, and the detective has a brief rant about left-handed/right-handed clues.
  • Parodied in Mark Twain's "A Double-Barrelled Detective Story," in which Sherlock Holmes deduces the following from a matchstick:
    "This: that the assassin was left-handed. How do I know this? I should not be able to explain to you, gentlemen, how I know it, the signs being so subtle that only long experience and deep study can enable one to detect them. But the signs are here, and they are reinforced by a fact which you must have often noticed in the great detective narratives—that all assassins are left-handed."
  • In The Fourth Protocol by Frederick Forsyth, MI-5 investigator John Preston is investigating Jan Marais, a South African diplomat he believes to be a Soviet agent, but the South African authorities have thoroughly investigated his background and found nothing amiss. Preston comes up with a plausible theory on how Marais was replaced by a Soviet agent while a prisoner in World War 2, but is told it's just speculation. Preston shows them a photograph of Jan Marais taken on a cricket pitch as a youth, where he's gripping the ball as a left-handed spin bowler. He says he's had Marais under surveillance for months, and the man is right-handed.
  • In a Gideon Oliver book, the victim was killed by a left-handed blow. But they don't have any left-handed suspects. There was one false alarm when Gideon saw someone writing in a mirror and accused them of being left-handed, but then realized that the mirror had flipped it, and the person was actually writing with their right hand. Revealed later on that the person actually was naturally left-handed, but had had it suppressed as a child so that he would grow up 'normal'. And during the highly emotional murder, had reflexively struck out with their left hand. The clue was the writing posture- according to the book, lefties-forced-to-be-righties often use a left-handed style with their right hand, and in the mirror, the person had been holding the pen like a lefty with his right hand.
  • Hercule Poirot twice ("The Market Basing Mystery" and "Murder in the Mews") used a variant in which the victim is left-handed, and committed suicide with a shot to the temple. A friend then framed the person they blamed for the suicide for murder by moving the gun to the right hand, thereby making the shot look impossible. (In the Poirot adaptation, however, the friend took the gun from the victim's left hand, then cleaned her handprint before placing the gun back on her left hand, albeit improperly.)
    • In the same Poirot adaptation of "The Affair at the Victory Ball", during the denouement at the BBC Radio station, Hercule Poirot reveals that Chris Davidson was the killer by the fact that Davidson was left-handed and the victim (Viscount Cronshaw) was right-handed.
  • Used extensively in The Man in Lower Ten by Mary Roberts Rinehart, where the detective is convinced the angle of the stab wound means the killer was left-handed. As it happens, the man the killer has framed is also left-handed, though he immediately tries to hide this fact. And later on, a Red Herring is arrested on the strength of his left-handedness, though the mistake is quickly discovered.
    "Stuart," he said sternly, "there are two very serious things we have learned about you. First, you jab your scarf pins into your cushion with your left hand, which is most reprehensible"...
  • In one Lord Darcy story, "A Matter of Identity", the detective looks at the location of a wound and reasonably concludes from the location that the killer was either left-handed or had a vicious right-handed backswing. Later investigation proves that deduction wrong: While the corpse was connected to a crime, his death was an accident, not murder - he fell down the stairs.
  • Not only do the Lord Peter Wimsey novels use the trope from time to time, but the books openly lampshade it. Most pointedly in Busman's Honeymoon, where the blow appears to have been struck left-handed, and a left-handed man comes under suspicion for a while, but it turns out that the blow was struck by a heavy weight swung from above, rendering considerations of handedness irrelevant.
  • In The Man in the Queue, by Josephine Tey, Inspector Grant spends a great deal of time deducing the handedness with which the killing blow was dealt, and then looking for someone who uses that hand, only to find out at the end that the killer is ambidextrous.
  • In Murder on the Orient Express, Poirot notices that the victim's stab wounds indicate that he was stabbed by both a left-handed and a right-handed person.
  • Used in The Roman Mysteries story The Slave Girl from Jerusalem.
  • Sherlock Holmes used this exactly once and it was handled somewhat more sensibly than usual: the victim was killed by a blow to the head (delivered with the strong arm) and the footprints indicated that the killer was standing right behind him.
  • To Kill a Mockingbird used this trope in the court-room scene. It made a lot more sense in this case, as the accused's left hand was badly mangled in a childhood accident and he couldn't use it. The actual strategy used was a little more complicated. The accuser said that she was held down and beaten, at the same time; something not possible when the alleged assailant only has one properly functioning arm. The main invocation of the trope, though, comes when the accuser has bruises on her right eye - it would be very hard for the accused to hit her on that side of her face when his functioning arm is on his right. (The accuser said that they were facing each other on the ground.) Unfortunately, despite the fact that this was overwhelming evidence that the accused was innocent, he was still convicted because he was black.
  • Inverted in the short story "Tomorrow Town" by Kim Newman: one of the suspects is ruled out because she's left-handed.
  • Played with in Towards Zero by Agatha Christie. The doctor notes that from the position of the body and the angle of the blow the strike would be very tricky to do right-handed - lampshading the trope at the time. Subverted when it turns out the blow was struck with the right hand - but it was a backhand blow from a star tennis player.

    Live-Action TV 
  • CSI, House, Law & Order: Special Victims Unit, and a Patricia Cornwell novel each did a more unlikely variant, though, where the killer had two separate sets of DNA, so saliva samples did not match blood or semen. (The reasons differed: in one, this was the result of a rare birth defect. In the Law and Order episode, it was the result of a bone marrow transplant.)
    • The birth defect version was probably Ripped from the Headlines, as there was an episode from a True Crime show that covered the same thing.
    • In the CSI episode, the killer's semen DNA did not match the swab in his mouth, but it did point to a sibling. All his brothers and cousins were tested and came back negative.
      • Sounds like they did their homework for a change. A "chimera" has 2 sets of DNA in different cells of his body, with both sets related in the same way brothers/sisters are related. It's basically the opposite of identical twins: instead of 1 zygote splitting in 2, 2 fuse into 1. As long as both are of the same gender this tends not to cause any problems for the child, otherwise the child might be inter-sex. The condition might be far more common than previously thought (most people never have their DNA analyzed, so they'd be completely unaware they have the condition). There is F.I. the real-life case of a woman who gave birth to several children that (according to DNA) weren't hers. The government moved in to investigate and officials were present when she gave birth to yet another child that wasn't hers. Nobody understood what had happened (the mother herself least of all) until they stumbled upon a doctor who knew about chimeras.
  • In the Angel episode "Harm's Way", while attempting to prove she didn't kill someone, Harmony uses the possibly-true fact that vampires tend to always bite on one or the other sides of their victim's neck.
    • Makes sense. When kissing, people have a preferred side they tilt their head to, vampires are usually human-based, so it might carry over. However, the first person to tilt his/her head sort of forces the other party to counter-tilt, so in case of a deliberate exposing of the neck...
  • In the Castle episode Tick, Tick, Tick, this tips off Castle that the case isn't solved. More justifiably so this time: killers may be more or less ambidextrous when it comes to bashing people with stuff, but fewer people shoot ambidextrously. Also, it wasn't a matter of "He's right-handed," it's more "He had the gun in his right hand seconds before the shot but was found with the gun in his left." Ambidextrous shooting or not, he simply didn't have time to switch hands before pulling the trigger.
    • In S7 episode "In Plane Sight," Lani manages to immediately identify a killer's handedness (left, natch) from a cell phone photo of a head wound.
  • Columbo: The killer in "Death Lends a Hand" was ambidextrous but seemed to favor his left hand, consistent with the victim's injury. But what really triggered Columbo's suspicion was the ring on the killer's left hand, which matched the shape of a gash on the victim's cheek.
    • In the MAD parody "Coldumbo" the lieutenant says "That's odd... the angle with which the killing blow was dealt indicates a right-handed killer, and when you were writing I noticed you're right-handed, doctor."
  • CSI also both subverted and plays this one straight. In one episode, Doc Robbins says that the whole "The Killer Was Left-Handed" thing is a myth but ventures a guess as to the handed-ness of the killer anyways. In future episodes, he plays it straight.
  • CSI: Miami
    • In one episode, one of the detectives inspects a hanging corpse and deduces that it must have been murder within seconds: "He is wearing a watch on his right wrist, which means has must be left-handed, but the noose was tied with a right-handed knot". This has a couple of problems. First, not everyone wears their watch on the side that they are supposed to, and second, tying a noose is a complicated action needing both hands, and it would be unlikely that someone had worked out a "usual" way to do it.
    • There's another episode where a serial killer carves a "Y" onto their victim's chests. When they've arrested a suspect, another body turns up, but the medical examiner determines that the "Y" is different; the previous victims were carved with the right hand, this one with the left. The suspect in custody is right-handed, but Calleigh notices that his sister wears her watch on her right hand.
  • Almost used in an episode of Diagnosis: Murder, where the killer must be right-handed. This lets the left-handed man off until it's revealed that everyone is innocent. Since someone must be guilty, it turns out the lefty is ambidextrous.
  • Lampshaded in an episode of Due South: An FBI Agent excitedly declares that they now know the blood type of whoever committed the crime. Constable Fraser points out that this narrows it down to roughly a third of the entire population of Chicago.
  • Ellery says this after surveying the crime scene in the Ellery Queen episode "The Adventure of the Judas Tree''.
  • Used inexplicably on Fortier where a contract killer uses an expensive Ruger specially modified for left-handed use and discards it at the scene. While it isn't all that rare to discard a "clean" murder weapon, leaving such a distinctive calling card on the scene where it will definitely be found is...odd.
  • The Golden Girls when the girls were participating in the Maltese Falcon Club, a murder mystery hotel, Dorothy solves one of the cases when the knife prop used to cut to the victim's throat was found on the left side of the victim (the "killer" only had seven seconds to commit the "murder" so it was cut and drop the knife quickly) and one of the suspects wore her watch on her right wrist.
  • Inverted in Law & Order: SVU the team is working on a case of a girl who was killed when she spied on a butcher shop with horrendous health and cleanliness issues. The manager who was caught quickly confessed that he killed her, but Olivia reviewed the girl's videos and noticed that the manager was left-handed, but the one who killed the girl was right-handed, and the real killer turned out to be an old lady who owned the butcher shop.
  • Lewis is another user of the victim variation — One for Sorrow has a victim found dead from an overdose of heroin with a needle mark in her left arm. As she had been a heroin addict, this at first didn't rouse that much suspicion... until it is noticed that all her old heroin scars are in her right arm, and her left hand has an ink stain.
  • Midsomer Murders: In "The Dagger Club", from his body, Kate determines that George Sommersby was grabbed from behind with the right hand and stabbed with the left, meaning the killer as almost certainly left handed. During the Summation Gathering, Barnaby tosses the killer a poker chip, which they catch with their left hand.
  • Monk: "Mr. Monk and the Garbage Strike" had an inversion of the first Agatha Christie example above. The left-handed victim was shot on the right side of the head. To make it look like a suicide, the killer wrapped the victim's left arm in a bandage to make it look broken.
  • Motive: In "Natural History", Betty determines that the fatal blow came from the front and struck the left side of the Body of the Week's head, meaning the killer was almost certainly right-handed. This clears the prime suspect, who is left-handed.
  • Mouse (2021): Mu-chi deduces one of the killers is left-handed from the angle of the knife.
  • A variant in Murder, She Wrote, "Funeral at Fifty-Mile". The victim was found hanging from the rafters in a barn. Later, when Jessica began investigating, someone placed a noose outside her window to scare her off. The noose that killed the victim was tied by a left-handed man, but the noose outside her window was tied by a right-handed man. This led Jessica to realize that either the killer was ambidextrous or that more than one person was responsible for the murder. It was the latter.
  • Played painfully straight on an episode of NCIS where the killer being left-handed cleared a murdered man's commanding officer and lover, despite the fact they knew that the killer was a woman in the Navy.
  • Pie in the Sky: Played with in "Who Only Stand and Wait". A left-handed person might still use his right hand if that's how the tool he's using was designed to be used.
  • In the "The Blind Banker" episode of Sherlock, the title detective concludes that an apparent suicide was in fact a murder because the left-handed victim had been shot on the right side of his head, something which would be rather awkward to achieve with your left hand.
  • Messed with in Star Trek: The Next Generation while Data and Geordi are doing one of their Holmes and Watson routines. An error in the holodeck messes with Data's deduction - a character is right-handed when he's meant to be left.
  • Whodunnit? (UK): The killer being left-handed is an important clue in "Pop Goes the Weasel". In an ironic twist, several of the panelists picked up the fact that the killer must be left-handed, but then completely failed to identify which characters were left-handed, resulting in three of them naming a completely innocent right-handed suspect as the murderer because they all thought he was left-handed.

  • Inverted in an episode of The New Adventures of Sherlock Holmes radio show. In the episode, Holmes and Watson meet a radiologist who casually describes his head assistant as adroit and his other two assistants as gauche, then chuckles that this is literally true as well as metaphorically. When the radiologist is (naturally) murdered by one of his assistants, Holmes deduces, in his brilliance, that it must have been delivered with someone using their right hand. Thus, only the "adroit" (right-handed) assistant could've killed the radiologist.

  • Parodied in Animal Crackers, in which the forgery substituted for the stolen "Beauregard" is determined to be the work of a left-handed painter.

    Video Games 

    Visual Novels 
  • Ace Attorney:
    • In case 4 of the first game, the gun bears prints from the defendant's right hand, while the photograph shows the killer holding it in his left.
    • In Case 1 of Justice For All, it is an Inverted Trope. The victim was left-handed, as evidenced by a baseball glove he was offered by the defendant, which is a plot point: the message written in the sand implicating her was written with his right hand.
    • Happens twice and in different ways in Ace Attorney Investigations: Miles Edgeworth:
      • The trope is subverted in case 3. Upon proving that the culprit that hit him with a sword did so with their right hand, Kay says that Lance, the person who Edgeworth suspects did it, is left-handed. Edgeworth, however, says that he simply used his non-dominant hand on purpose to throw suspicion away from him, stating that swinging a simple prop sword is easy, no matter what hand you use.
      • Inverted in case 4. The gun was used with the right hand, but the person who held it was a lefty, as demonstrated by another piece of evidence. This leads Edgeworth to conclude that another individual had to fire the gun. At the same time, it's also played straight, as at the time, he was being suspected of killing the case's other victim in a Mutual Kill. The fact the gun was in the wrong hand is, as noted, what gets Edgeworth to realize a third party was involved in the killings.
    • Another inversion in the DLC case of Spirit of Justice In which an assertion is made that the victim is suspected of writing a message. However, it's later proven that the victim is left-handed thanks to the fact his intended murder weapon was wielded in his left hand, and that the message could only have been written with the right hand.
  • Played with in Danganronpa V3: Killing Harmony, where the killer being left-handed isn't directly related to how they killed the victim, but it does prove their guilt. In Chapter 4 during the trial, Gonta Gokuhara is the only one who could've killed Miu in the virtual world, but he claims to have no memory of doing it, and (by his point of view) he's telling the truth. But when logging into the virtual world, everyone had to plug the "consciousness" and "memory" cables into the correct sockets on their headset. Miu states that she has no idea of what would happen in someone were to plug the cables incorrectly, but she guesses it would definitely not be good, and we later learn that it causes memory loss. Gonta got confused on how to put the wires onto the headset, so he relied on Himiko, who had to remind herself that "right is the hand you hold your chopsticks with". Unfortunately, Gonta is left-handed...

    Western Animation 
  • An episode of Ben 10 had a Kangaroo Commando-themed rollercoaster blow up. The actor who played Kangaroo Commando accused his rival of blowing it up, the only evidence being a right-handed glove. Gwen points out that K.C's rival is actually left-handed, as all his sketches are drawn with the left hand.
  • In one episode of Fillmore!, the hall monitors (yes, it's that kind of show) find that someone has been shredding other students' important papers. From the angle of the shreds, they determine which hand the shredder used to place the papers in. Turns out, it was all of the victims, working together to frame a non-existent shredder.
    • Also, the episode where someone was tagging the bathroom stall doors. Fillmore figures it out because the graffiti on the stalls was written with a marker, with each letter overlapping the letter to the right. This meant the graffiti had to be written from right to left in order to prevent smearing and thus the culprit had to be left-handed.
  • Gravity Falls: When someone beheads Stan's wax statue, Dipper and Mabel play detective to figure out who it was. Manly Dan, a lumberjack, identifies the "murder" weapon as a lefthanded axe, so they focus on identifying which of their suspects are lefties, which narrows it down to one. He has an alibi. The real culprit turns out to be the animated wax statue of Lizzie Borden, making the handedness clue meaningless.
  • In an episode of Scooby-Doo! Mystery Incorporated, the gang catch the "Dreamweaver" because he was the only left-handed suspect.
  • There's a variation in Steven Universe that is a big hint that a major backstory event was not how history recorded it- Rose Quartz is left-handed, or at least wielded her sword in her left hand (with her shield in her right). When Garnet recounts the story of how Rose shattered Pink Diamond in Your Mother And Mine, the Rose Quartz in the flashback wielded her sword in her right hand and did not have her shield at all. Because it was actually Pearl, who is right-handed and could not use Rose's shield as it was her gem weapon.