"Encyclopedia Brown? What a hack! To this day, I occasionally reach into my left pocket for my keys with my right hand, just to prove that little brat wrong."This is a specific kind of artistic license, where a pivotal clue in solving a mystery or puzzle is actually erroneous. This is related to Conviction by Contradiction, where a single thing wrong with an alibi is sufficient to prove guilt, but goes further: the key that makes the claim or alibi wrong is itself factually incorrect. For example, a guy's alibi is that he was caring for his pregnant mule, and he is immediately revealed to be lying, since mules can't get pregnant. We've got him! To the jail! Not so fast: while they're rare, fertile female mules do exist. Thus, there's a problem with this "revelation": it's simply wrong. When adding examples, keep in mind that a fact has to be actually wrong to qualify for Conviction by Counterfactual Clue. If there's simply a way to explain away the objection without calling factual rightness into question, it's Conviction by Contradiction. Many examples, especially ones with complex contexts, have some aspects fall into one, and others into the other. This can be sometimes excused by Science Marches On. In many cases, the "clue" started out as Conviction by Contradiction, then science marched it right over here. When this happens, but the ultimate conclusion is demonstrated to be correct, it overlaps with Right for the Wrong Reasons, especially when other clues in the story are skipped over, but are both factual and more useful.
— ericbop, MetaFilter
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- A common one seen in multiple detective series is the unwavering belief that all women are physically weaker than all men, which is commonly brought up as a foolproof alibi. Even when there's an elderly, overweight or disabled man in the room who doesn't get the same courtesy. Especially headache-inducing in the Moonlight Sonata case of Detective Conan, where a female doctor is written off as a suspect because she's petite with thin arms and couldn't have lifted the bodies. (Each of which are taller than her and would require quite a feat to move around the way they did.) Then when it's found out "she" is actually a crossdressing man this alibi immediately vanishes, even though he's still the exact same muscleless Bishounen waif.
- A mildly confusing case in The Kindaichi Case Files where Hajime reveals the culprit by pointing out that tomatoes are not fruits. Some people can be forgiven if they yelled "tomatoes are fruits you idiots!"—the truth is that while tomatoes are considered fruits (seeds and all), they are considered vegetables in both culinary arts and most tax codes.
- In the 1980s and 1990s, the Swedish edition of The Phantom had a page of reader-submitted material, of which one of the more popular were crime mysteries (see Conviction by Contradiction for more details). One of these had the culprit give himself away by referring to the banana as a fruit. Even though banana trees are herbaceous plants, a banana is biologically considered a fruit. Even when using the culinary term for fruits (which is probably the term most people outside of the fields of biology, botany, and horticulture are familiar with), this still doesn't exactly excuse the conviction, as the banana is one of the most classic examples of a "Culinary Fruit." (For a more specific description, a culinary fruit is any edible fruit that is sweet. Biologically, a fruit is a plant structure that contains seeds. This is why things like tomatoes, peppers, eggplant, and cucumbers are classified as fruits by botanists, but not by chefs.)
- The trope is invoked and lampshaded in Welcome to Tranquility. Emoticon is in jail and being questioned with regards to the murder of Mr. Articulate, a crime-solving member of the community who was legendary for his intellect, wit and long and storied history of traveling the world. However, Emoticon points out that a lot of the stories of his adventures were "culturally insensitive", and he recounts one of the detective stories from Mr. Articulate's youth that always stuck in his mind: Mr. Articulate discovered the identity of the murderer because the "Korean" man at dinner left his chopsticks in his bowl of rice, something no actual Korean would do since it is a symbol for death and, therefore, he must not be Korean, but Japanese instead, and thusly the killer. However, Japanese culture has the same custom. "So the ending doesn't work. It's a cheat."
- Of course, Koreans eat rice with a spoon, so there's one more reason it doesn't work. They eat other dishes with chopsticks.
- The British "Adult" comic Viz ran parodies of this, among others the "Spot The Clue" strip. A whodunnit situation is shown, with the reader being asked to work out who the perpetrator is. Each time the villain is the one who made an innocuous error, ranging from incorrectly describing the era of a piece of furniture, to claiming to have been sending emails on a piece of hardware that everyone knows is too unreliable to work.
- Lampshaded by "Inspector Bougret", an occasional feature of Gotlib's strip Rubrique-à-Brac. Presented with two suspects, one of whom is blatantly guilty, Bougret accuses him for an absurd reason. In one case, the murder weapon is a brick of a material unknown on Earth; Bougret accuses the one who willingly shakes his hand, because only an extraterrestrial would shake a cop's hand — not because he's visibly not human.
- One Jimmy Olsen comic featured Jimmy crossdressing to test the detective skills of his fanclub. They found him out in part because "Jackie" had tied a bowtie into a garter, to show "herself" as a member of the club, and according to them, "girls don't wear neckties and never have the practice to tie them that well." This is probably news to the millions of women who help their boyfriends, sons, or husbands with getting their ties on.
- An issue of Power Girl featured an exploration of this, when Bruce Wayne gives the corpse of a supposed suicide victim an autopsy. He points out that the bullet wound is on the forehead, at which Dick Grayson points out that it's not unheard of in suicides. He then points out that the exit wound suggests the bullet came from straight-on, and Dick again points out that it's weird, but not impossible. Then he points out that the angle suggests the gun was being held in the victim's left hand when they were right-handed, and Dick points out that the victim was a Badass Normal and reasonably able with his left hand. Bruce responds by pointing out that, yes, it's possible that the victim held the gun to his head at a bizarre angle with the wrong hand, but it's not likely, and Dick keeps focusing on the least likely possibility - which is what causes them to conclude that they're being influenced mentally. And just to nail the coffin, he gives a much less disputable bit of evidence; namely, the bullet hole is too neat for a gun-to-the-head shot.
- In "Ego Trip", John Byrne's story in Batman 3D, a receipt is found that mentions delivery of "zzxjoanw" to the victim. The cops figure it must have been some garbled message to someone named "Joan". Batman, armed with encyclopedic knowledge, knows that a zzxjoanw is actually a Maori drum and deduces that the victim was a collector of obscure musical instruments. The problem is that in real life, "zzxjoanw" is actually a fictitious entry in a 1903 music encyclopedia that managed to make it into two other books of "interesting words" over the next 50+ years, and no such instrument actually exists (Maori doesn't even have the letters Z, X, and J).
- In an old Slylock Fox Mystery puzzle, Slylock investigates some stolen roses. Another character has some roses in a vase that she claims were a gift from her boyfriend. He deduces that she is lying, and that she is actually the flower thief. The reason? Well, aside from the fact that she is one of the recurring "villain of the week" characters, the roses still have thorns on them, and a florist would have removed them before selling the roses. Never mind the fact that many florists don't remove thorns from flowers because doing so makes them wilt faster (as does excessive handling of cut flowers, so thorns shouldn't be too much of an issue). Nor the fact that her boyfriend could have picked them from his own garden and given them to her, or that he might have been the flower thief, and her story about receiving the flowers as a gift could still be true.
Films — Live-Action
- In The Spider Woman (1944), Sherlock Holmes deduces that a series of apparent suicides were really murders because "suicides invariably leave notes behind them," and none of these people did. Actually, no more than about 20% of suicides leave a note.
- In the movie Soultaker, a cop investigating a fatal car crash finds it odd that the doors of the car are both wide open. He doesn't buy that a closed, even locked car door could fly open if the car were to crash, and asks his partner, "What are the odds?" (It's because the ghosts of the passengers opened them.) In reality, the odds of both doors of a two-door car being flung open in a high speed head-on collision are pretty goddamn good. This didn't escape notice when the movie was featured on Mystery Science Theater 3000.
- From Two-Minute Mysteries by Donald Sobol.
- The "mule" clue was used in "The Case of Molly's Mule". Sobol would later reuse this clue in an Encyclopedia Brown mystery called "The Case of the Gold Rush". The first time can be excused as a common mistake, but the second time less so.
- A Two-Minute Mystery had a deaf witness's testimony that he read the suspect's lips and took special note of it because the suspect was whispering called into question, because supposedly, he shouldn't have been able to tell the suspect was whispering. However, whispering is just when instead of using your vocal cords normally, you create turbulence with them, producing a hissing sound. This then requires you to use your lips and mouth to create sounds that your vocal cords normally would, and is very noticeable to a lip reader. You can easily demonstrate this by saying the same word as a whisper and in normal voice, and feel how different your mouth moves. Then try freezing your jaw and lips in place and speaking, something you can do mostly understandably with operating your vocal cords normally, but you can't produce meaningful sounds at all if you try it while whispering.
- In one Two-Minute Mysteries story, a man relates how he leaned over his train bunk and read a headline on the newspaper the man below him was apparently reading. His companion deduced that the man with the newspaper was the perpetrator, because the only way the first man could have read the headline is if the newspaper was held upside-down (and therefore upside-up, relatively speaking, to the first man's eyes.) However, many people can read upside-down text just fine, especially if the text is in a large font and the message short (like a newspaper headline). Many dyslexics can read upside down almost as fast at reading the normal way, sometimes even faster. Even without any skill at it, everyone who can read can decipher upside-down print letter by letter. It may take a few minutes, but what's time to someone sitting bored in a train? Or, even easier, the top half of the paper may have been folded back while the man read the bottom.
- In "Murder at the Zoo", Haledjian meets with a zookeeper after a doorman working at the zoo is found killed. The zookeeper claims to have been alerted to the murder when he heard the scream of a giraffe, since one of them had been caught in the crossfire. Instantly Haledjian declares him to be the real murderer, because according to him, giraffes have no vocal cords. In reality, giraffes have vocal chords so large that they usually make sounds too low in pitch for humans to hear. This is why biologists for a long time thought that giraffes made no vocalizations. While adult giraffes usually seem silent from our perspective, calves can be quite noisy.
- An alleged suicide note from a linguistics professor is determined to be a fake due to some grammatical "mistakes" that a true linguist would never make, including the use of a split infinitive. The correctness of split infinitives is a matter of great debate; while some do abhor them, many grammarians have no problem with them at all. And that's before you have to wonder if a person contemplating suicide is in the correct frame of mind to even consider proofreading their own suicide note.
- Encyclopedia Brown, the former Trope Namer, also by Sobol, often bases the solution of mysteries on assertions that a certain event could not have happened as described for a particular reason. In some cases, the reason would make the event unlikely, but not impossible. Other times, the reason is simply false.
- The page quote comes from a mystery where one kid with a cast on his left arm is accused of stealing some keys, and in fact they're found in his pants pocket in his locker. However, the "proof" that he didn't do it is found in that the keys are in his left pocket, and, according to Encyclopedia, it's impossible to put keys in the opposite pocket of the hand they're in while running, as Bugs Meany claims happened. It might be more difficult for some than others, and there would be very little logical reason to do so, but it's certainly not impossible for everyone. Though in a technical subversion of this trope, the pants pocket scene isn't actually the final conviction per se.
- In one case, the culprit's alibi was that, when he walked past the victim's house, he heard the electric clock (which was unplugged when the crime was committed) ticking, the contradiction being that electric clocks don't tick. When this was first written, (back in the 1970s), this was Conviction by Contradiction, though questions like "How loud would it have to be ticking to be audible outside the house?" and "Exactly how is this an alibi anyway?" might arise. Today, we can skip straight to the fact that some electric clocks — particularly analog clocks in which the second hand jumps from one mark to another and an early kind of digital clock where numbers were written on flaps that showed in succession (as shown in Groundhog Day among others) — do make sounds that, while distinct from pendulum-regulated clocks, are described as "ticking". Additionally, some digital clocks that indicate seconds will play an artificial ticking sound.
- One involving a sword from The American Civil War. The guy hawking it claimed it was authentic due to the engraving showing that it was given to Stonewall Jackson by Robert E. Lee after the First Battle of Bull Run. The 'correct' answer was that the sword was fake, because nobody would have called it FIRST Bull Run until there had been a Second Bull Run. However, given how long it can take to commission, make, retrieve, and engrave a sword, it's entirely possible that the second battle a year later either already happened or was soon coming, necessitating the need for specificity. In fact, there are two other problems with the story, both of which would have been better pieces of evidence. One, Confederate forces did not refer to either battle as Bull Run at all, but rather as the Battles of Manassasnote , and two, General Lee wasn't present for the First Battle of Bull Run/Manassas: the Confederates there were led by P.G.T. Beauregard. Sobol pointed this latter fact out in later editions.
- Encyclopedia Brown pinned a crime on a magician because he was wearing short sleeves. He claimed that all magicians wore long sleeves so that they could pull objects out of them... except good magicians don't need anything of the sort. Many, in fact, wear short sleeves solely to impress people with the undeniable fact they have nothing up them, and at least one group performs magic in the nude. There are entire styles of magic that depend on (for example) marked cards, psychological tricks, or props with trap doors, for which sleeves are completely useless. Even in cartoons, stage magicians as a whole tend to have the catchphrase "nothing up my sleeves", as they roll them up before a trick.
- One case was "solved" (by Sally, not Encyclopedia) because a couple sat in a restaurant with the man's back to the wall rather than the woman's, from which Sally deduced that each was actually a member of the other gender in disguise. This is because of a rule of etiquette that the woman should sit against the wall, so she can see and be seen. For this to be evidence, it would have to be the case that people followed this "rule" with no, or at best, very few exceptions; only Sally had ever heard of it. This same solution supposes that the victim is a woman so strong only a man could've knocked her out with one punch, ignoring the victim's own strength and the possibility for other women to be that strong.
- From a meta perspective this "solution" also ignores what a big piece of the books' internal logic "girls can be even tougher than boys" really is. The canonical reason the bullies Encyclopedia outsmarts don't try to get even by just punching his teeth out is his partnership with Sally, who beats up anyone who tries. The books go so far as to actually call her his bodyguard whenever they explain this.
- Another solution was based entirely on the supposed 'fact' that roosters only crow when they saw light, apparently based on the urban legend that roosters crow at sunrise. The crime was a con man trying to convince kids he found a way to make roosters crow on command, but actually uncovering the cage so they saw light and thought it was sunrise; he claimed that he would soon improve the device to make hens cluck on command, and that whenever hens clucked, they laid an egg. Anybody who has been around a rooster for an extended period of time will know full well that they crow whenever the heck they want, whether the sun is out or not. And, of course, the hen part of his story should have been clearly false, especially since he was targeting the con towards chicken farmers.
- One solution in "Encyclopedia Brown Takes the Cake" relied on the fact that the culprit had used glycerin tears that fell from the outside corners of her eyes instead of the inside, thus revealing them to be fake, as "If only one tear falls, it will run from the inside corner of the eye, by the nose, and not from the outside corner." Only, none of that is true; how tears flow from a person's eyes is a function of the physical shape of their eyelids, nose and cheek.
- In Encyclopedia Brown and similar riddles there are puzzles about coins being a forgery because the name of the ruler is King Bob the First or similar. Obviously, no monarch referred to himself as The First, right? Except that they did—either to show that they're first among equals, or because they had a son named after them, or because they would indeed be the first monarch with that name, as was, for instance The Pope John Paul the First. Or recently abdicated Juan Carlos I (John Charles the First) of Spain. Interesting case that of Charles the First of Spain and Fifth of Germany, or James the Sixth of Scotland and First of England.
- In the first case, Encyclopedia Brown deduces that the blind witness is lying because he has a newspaper in his room. Ignoring all the reasons one might have a newspaper they can't read in their room, it isn't even necessarily true that blind people can't read newspapers. Most legally "blind" people still have some amount of vision, and depending on the exact nature of the vision loss, it's entirely possible to be able to read a newspaper (perhaps with magnification).
- Sherlock Holmes:
- In "The Adventure of the Blue Carbuncle", Sherlock Holmes deduces that the owner of a lost hat must be an intellectual, because it is a big hat, and so he has a large head. Again, it's largely Science Marches On; that was actually a serious scientific theory at the time. Even in the context of the era, it ignores the possibility that the hat's owner might simply have a very thick head of hair atop an average-size head, or a simple preference for oversized hats.
- In "The Adventure of the Priory School", Holmes deduces the direction a bicycle was heading by the fact that the hind tire track passes over the front tire track. However, the hind tire would pass over the front tire tracks regardless of the direction (unless the bicycle was in the process of turning at the time). This article explains an actual way of figuring out the bicycle's direction.
- In a Mike Mist Minute Mystery by Max Allan Collins in the early 1980s, the title character supposedly identifies a crook because she claimed that she cashed a check using an automatic teller machine, which Mike claims is impossible. Here, the readers wrote in to note that it's done all the time; you enter the correct amount of the value of the check into the machine as a deposit and you are free to withdraw from that amount. And of course, Technology Marches On: you can now deposit a check into (some) ATMs, and the machine is sophisticated enough to scan it and correctly parse the writing as a check amount.
- One entry in The Armchair Detective series stated that one true way of knowing if a pre-World War II telegram is false is if the phrase "World War I" or "The First World War" is ever mentioned, on the assumption that nobody could have foreseen a second World War before it started. However, it was used by some almost immediately after hostilities began. Note that the series in general isn't particularly prone to this. In his defense, those were not common terms, and would hardly be included in a telegram where they could easily say "The War" or "The Great War" with fewer letters. It may not be rock-solid evidence, but it's a good reason to be very skeptical.
- It should be noted that using them as the actual name of the War would be even more suspicious—although the First World War was, indeed, used, it at first was more of a descriptive term (IE, describing the War as the first World War in contrast to previous, non-global, wars, and, as in the case of the first recorded use of the term, the early-war term 'The European War').
- This is Science Marches On, but one of Isaac Asimov's space mysteries hinged on the fact that one side of Mercury always faces away from the sun, because at the time it was reckoned this was true. Later research proved this wasn't the case (Mercury does rotate, albeit extremely slowly at 1.5 local days per local year), which Asimov acknowledged once he learned it. Unfortunately, he couldn't see any way to amend this clinching evidence without completely re-writing the story, so he added a tongue-in-cheek afterword stating that he wasn't going to change his perfectly fine story just because some scientists "changed their minds", and it's really all their fault if you think about it.
- In the Monk Tie-In Novel Mr. Monk in Outer Space, one of Monk's deductions that makes him conclude that a person was killed in a different hotel room and moved downstairs to a different room in a maid's cart hinges on the fact that insulin must be refrigerated. Except it doesn't; diabetics commonly keep vials of insulin currently in use at room temperature, usually due to the discomfort of injecting cold insulin. He also incorrectly states that all diabetics take insulin, when some Type 2 diabetics can control their diabetes through diet and exercise alone, and most can control it with the help of oral medication.
- Refrigerating insulin mostly has to do with preserving it longer. Doctors recommend keeping insulin at room temperature for a month at most, while keeping it cold extends this to six months.
- One of the subcases in Mr. Monk and the Dirty Cop that is mentioned in a few paragraphs takes the Encyclopedia Brown example used as the page quote. What is known about said case is that it is a man who tripped over a crack in a parking lot and broke his arm, which is locked at a 90 degree angle according to his doctors, yet it is possible to see his car keys in his right pocket, which should be inaccessible to that hand. For all we know, this person could just easily grab their car keys with their left hand—but it is at least good reason to look closer and see if the man's arm were truly injured.
- The above also ties in with Monk's general tendency to avert this trope as Monk will often quickly find a series of points that leads him to believe that a suspect is the culprit but more often then not most or all of them could be explained away very easily. Monk will agree that all of the counter points are valid but use their improbability as the basis to do further investigation for actual proof ("He's the guy. I don't know how, but he's the guy.").
- One Encyclopedia Brown-esque story concluded that the suspect was obviously lying because he claimed he was at a laundromat putting clothes into a top-loading dryer. The detective claimed that all dryers are front-loading. This is incorrect; top-loading models existed on the market even in the time period when the story was writtennote .
- This happened with Encyclopedia Brown himself. Bugs Meany lied by copying another kid's true version of events, changing washer to dryer but otherwise using the exact same words. The first kid said he'd put the clothes in from the top, and Bugs copied that detail.
- In the battle between Archmage Gromph and Dyrr the lich in the War of the Spider Queen series, Gromph realizes Dyrr's shapeshift spell means he's not undead anymore, so negative energy spells can and do work on him. The kicker? He'd polymorphed into a construct, which is still immune to negative energy and a Lich, unlike most undead, CAN polymorph himself as an explicit part of the runes.
- In one of the Avatar Trilogy novels, a ghostly figure appears in front of Cyric's mercenary band and threatens them. Cyric, observing that none of the witnesses has aged as a result, concludes that the figure isn't a genuine ghost (which had an aging aura under then-current D&D rules), but a harmless product of wild magic. Not only is there no clear reason for him to assume a product of wild magic would necessarily be harmless, but there are several dozen other ghost-like creatures in the Forgotten Realms Verse that it could have been, that would not age witnesses yet would be extremely dangerous in other ways.
- Woody Allen parodied this in a story called "Match Wits with Inspector Ford", where Inspector Ford deduces that a man didn't kill himself, because there was cash in his pocket, and someone who is about to commit suicide would use a credit card.
- In Murder on the Links, the second Hercule Poirot case in terms of internal chronology (though probably not of publication order), Poirot sees a stage act consisting of twin sisters (one blonde, one brunette) and deduces that one of them must be wearing a wig. Because of course it's impossible that twin sisters could be fraternal, or that their parents could be a blond and a heterozygotic brunette (or two heterozygotic brunettes).
- The hair dye point still holds, but the sisters are repeatedly described as perfectly identical (and thus probably not fraternal twins).
- There's an interesting case in Agatha Christie's Appointment With Death where one of the clues is demonstrated as false within the story itself, and the author probably didn't even notice. Five relatives of the victim are all suspects. The murder was done using a syringe, while the victim was known to take potentially deadly medication. Poirot says that the use of a syringe proves that none of the family are guilty, because the family had access to the medication and would have staged an accidental overdose. Except that just a few paragraphs before Poirot announces this deductive proof, a member of the family clearly says he actually was planning to kill the victim using a syringe.
- In The Palace Tiger, a vital clue hinges on the murder weapon being a bagh nakh (Hindi for "Tiger's Claw"), which leaves a broken tiger claw in the wound. The weapon is described as being an actual preserved tiger paw mounted on a handle, hence the clue. In fact, the bagh nakh is a set of metal claws attached to rings which slip over the fingers; the name is metaphorical.
- In a Nancy Drew book, a dog eats a box of chocolates and dies—this is treated as a plot point because the box of chocolates shouldn't have killed the dog alone. Actually, chocolates are not good for dogs! While its toxicity to them is often exaggerated, a full box of chocolates could easily poison a small pooch to death (white chocolate is the only exception, as it contains no cocoa solids and therefore has only negligible amounts of the toxic substance). In fact, it's a somewhat frequent cause of accidental death for dogs, because despite it being bad for them, the bastards love how it tastes and gorge themselves when able to.
- Zigzagged in The Dresden Files book, Ghost Story. While confronting Aristedes Butters pretends to be a Warden. Aristedes notices that Butters doesn't have a sword, and therefore isn't a Warden. This is not actually accurate. They are currently unable to make new magic swords, so younger Wardens don't have them. Dresden notes this, but since neither Aristedes or Butters know about this, it doesn't matter that he's technically wrong.
- In the Mary Higgins Clark novel While My Pretty One Sleeps, the as-yet unidentified killer notes that he made a major error in dressing his victim's body and realizes that the protagonist will realize it, given her knowledge of fashion (she's a designer and designed the outfit that the woman is dressed in, but he got the shoes wrong, a mistake that the victim, herself a designer, wouldn't have made.)
- A rather amusing in-universe example in Star Trek: Deep Space Nine. When O'Brien is marked for death by some crazy aliens because he's one of the last people alive who knows how a forbidden superweapon works, they send a bogus video back to the Federation that shows him dying in an accident. His wife realizes something's fishy because he's drinking coffee in the video and she knows he never drinks coffee in the afternoon, when the video was supposedly taken. But then after the plot is foiled and Miles comes back home, as he's settling in he asks for a cup of coffee. She reacts with astonishment, and he says he drinks coffee in the afternoon all the time!
- In an episode of Judge Judy, a man is trying to collect money owed to him by a woman who rented a room from him. He says he provided her with an invoice each month and brought copies showing how much the woman owed him. The invoices had the invoice date on each of them, but they also had a date in the header or footer showing the date they were printed. Judge Judy points out that these invoices are fake because they all have the same date. The guy made the argument that the invoices were created when he said they were, pointing to the invoice dates, but the other date was the current date, the date he printed them. Judy said something like, "I'm not stupid, you know," and ruled in favor of the woman who owed him the money, because apparently to her it's impossible that anyone printing a copy of something would record the date the copy was printed. Never mind the fact that Microsoft Word has a feature where a date within the document can automatically update itself each time the file is accessed.
- Sherlock is often guilty of this.
- "A Study in Pink" has Sherlock deduce that the former owner of John's mobile was his brother and a drunk runs entirely on these. He assumes that people not wanting to pay the entire rent of a flat would be frugal in every other aspect of their lives despite flat mates being quite common among people of varying financial backgrounds. He assumes that older people don't have cell phones, which was sort of true in the time period the show was produced but the phone being a gift explains that. The scratches on the power connection are a shout out to the same deduction being used in the original stories but for watch winding. However as most cell phone owners can attest, the tiny plug of that style of cell phone is difficult to find and people often plug their phones in in the dark, most cell phones over six months old will have scratches around the outlet, whatever the owners intoxication level. In fairness, he did admit the last one was a "shot in the dark," and later explicitly stated he wasn't expecting to get everything right. Parodied in this skit.
- "The Blind Banker" has Sherlock deduce that a suicide was actually a murder because the person was left-handed and was shot in the right side of the head and it would be awkward to twist the left arm around to right side of the head. This runs on the assumption that left-hand dominant people are completely incapable of using their right hands. Putting a gun to your head is a simple motion easily completed with the non-dominant hand. There's also the fact that most guns are designed for right-handed people, and as a result it's not uncommon for left-handed people to shoot right-handed — Watson himself is shown writing with his left hand and shooting with his right. On top of that, powder burns and blood splattering could have easily revealed the distance and angle of the shot to rule out suicide, which makes the police unquestioningly buying Sherlock's deduction unrealistic.
- Another episode has him deduce that a man must be cheating on his wife because his phone had a waterproof case, reasoning that because he didn't have the tan of a man who works outdoors, that must mean he takes his phone into the pool with him, which must be because there's something on it he wants to hide from his wife, which must be text messages from a secret lover. Because apparently there's no other possible reason to take your phone into a pool.
- Would you believe CSI is accused of this?
- In perhaps the most memorable chain of cases ever, the identity of the Miniature Killer is revealed by bleach, the only linking thing in the four mini-crime scenes. However, one of them was listed not under the name "bleach", but by its chemical name, NaCl. NaCl is sodium chloride (table salt) while bleach is sodium hypochlorite (NaClO).
- Lampshaded in another episode. Captain Brass decides to reopen an "accidental death" case after he sees the supposedly bereaved husband coming out of a club to hop into a brand new sports car. He later tells the husband that his (Brass') suspicions should've been aroused earlier—when he interviewed the husband, the man said that he "loveD" his wife, and Brass' experience was that innocent people never referred to their loved ones in the past tense so soon after their death. note While this obviously (as the accused's lawyer specifically points out) means little legally, it did give Brass more reason to pursue his new suspicions.
- And there's an episode where Catherine suspects a mother assisted in a murder her son took part in because a body bag found at the crime scene was neatly folded, and Catherine said, "Teenagers never fold things, mothers do!" Apparently clean freak teenagers (or sloppy mothers) do not exist in Catherine's mind.
- In another episode Catherine (again) catches a woman who killed her daughter by which way the woman was looking when she was talking to Catherine. Catherine deduces that the woman was looking left and therefore lying. The woman did confess after being caught, but had she not, their whole case would be hinging on this, when people who are experts on lie detection and reading microexpressions say that statistically people are more likely to look straight ahead when they are lying.
- One episode of NCIS has Cate determining a suspect is lying by the same logic. He looks to his left, so he's obviously recalling a concocted story. Had he been telling the truth, he would have looked to the right.
- In the Leverage episode "The Homecoming Job," Sophie realizes that a Sleazy Politician lied to her about something because he looked her right in the eye when he said it. According to her, the only time any man ever looks a woman in the eye is when he's making a special effort to lie to her. A bit better than other examples on this list, because this one was more a snarky line than a serious deduction. It may have been snark, but it was also based on truth. Some of the latest research indicates that people who are lying are more likely to look you in the eyes to make you believe what they're saying and people who are comfortable in what they are saying tend to look in any direction they feel like because they don't need to fully concentrate on what they're saying.
- In Jonathan Creek, "The Curious Tale of Mr Spearfish" is resolved when Jonathan notes that two blue-eyed parents can't likely have a brown-eyed child and thus a character in the story is adopted and is secretly of Royal Blood. This is false.
- An episode of Columbo titled "An Exercise in Fatality" has a key piece of evidence that a fake suicide was really a murder hinge on how the victim's shoes were tied. This actually could have been reasonable evidence, except that the way the evidence is framed and explained is completely self-contradictory and counter-factual. The problems with Columbo's explanation are as follows:
- Firstly, Columbo explains that when right-handed people tie their own shoes, the big/top loop ends up over the big toe every single time — which suggests that people tie their shoes with a different dominant hand depending on whether they're tying their right or left shoe, as opposed to using the exact same process on each foot. This is completely wrong, as any non-ambidextrous person who ties their shoes would know.
- Secondly, Columbo explains that the victim's shoes were tied with the big/top loop over the little toe, indicating that a right-handed person must have done up his shoes for him, because they would be doing their usual action backwards. The problem with this? The victim was clearly stated and shown to be left-handed, thus this supposed evidence doesn't contradict the notion that the victim tied his own shoelaces, because nothing would be "backwards" about the way his shoes were tied.
- Murder, She Wrote:
- A man dressed as a Roman Catholic priest is giving Jessica what might be important information. Jessica quotes Henry David Thoreau, but attributes the quote to St. Thomas Aquinas. The "priest" doesn't call her on it — and supposedly any real priest would know. Apparently imagining that all Catholic priests immediately recognize everything St. Thomas Aquinas did not say and always call people out on it, Jessica "knows" he's not really a priest.
- In another episode, Jessica and the local sheriff find a matchbook inside a woman's car after the car was pulled out of water with the woman deceased. The two argue as if the only and mutually exclusive possibilities are that the woman stopped there the night she died, and that the matchbook was planted or placed there. This is treated as an important clue, as if there are no other ways a person might have some detritus like a matchbook in their car.
- In a first-season episode, Jessica solves a murder by realizing that the police Lieutenant who was investigating the murder dismissed a spot where a framed item had been removed as having been nothing more than a family picture could only have known that if he had been inside the home prior to being summoned, as the victim's daughter had removed the picture as soon as she found her father dead. Except that he could have potentially learned that from the various people who were in the house when the body was discovered. This is a bit downplayed, though, as the Lieutenant does not think to offer this excuse and instead pulls a gun — the murder weapon — on Jessica, who (after he is disarmed) acknowledges is the only real piece of evidence.
- This is often invoked on The Listener when Toby has to make up some story of how he figured out a person was lying to him since he cannot reveal that he figured it out through telepathy. Knowing it would never be accepted as evidence in a court of law, Toby and the cops must then find other evidence in order to make an arrest.
- An interesting in-universe example in House. House suspects an amputee is lying about being a Vietnam veteran. When he discovers that the guy is from Canada, he confronts him and triumphantly points out that Canada didn't send troops to Vietnam. The guy angrily points out that Canada did send troops to enforce the Paris Peace Accords, resulting in him losing his hand to a grenade. This also fails to account for all the Canadians who enlisted in the US Military and volunteered to go to Vietnam (around 30,000 in all), just as many Americans volunteered to fight for Canada before the USA entered WWI and WWII.
- Criminal Minds:
- In "Machismo", the BAU travels to Mexico to assist the local police force in arresting a serial killer that is targeting elderly women. They find that the killer is also a previously unreported serial rapist, and that he is killing the mothers of the women he raped, because each of the elderly women's second surname is the same as the younger women's first surname. In Spanish naming customs, every person has their father's first surname as their first, and their mother's first surname as their second—the opposite to what happens in the episode.
- Reid insists that a person who kidnapped a child and then makes threatening phone calls to his parents utilizing a voice changer is in fact a woman, because the caller didn't taunt the FBI, therefore the kidnapper isn't competitive and ego-driven, and because they insisted on describing certain aspects of the child's clothing, such as his shoes being teal, the idea (which Reid actually spells out) being women wouldn't be competitive and ego-driven, and only women notice or call attention to small details like colors. He turns out to be completely right on all points as regards the perpetrator, which, of course, ignores the alternate possible explanation that people are individuals and plenty of men are not competitive by nature and notice small things like shoe colors. The kidnapper having been a shoe salesman might've been an interesting reveal.
- An in-universe one: In "A Higher Power", the BAU is called to investigate a recent spike in suicides in a small community in Pittsburgh, the victims of which had lost their children to a huge fire months prior and had apparently succumbed to their grief. They are called in because the lead officer's brother was one of the victims and the cop is adamant that his brother would never have killed himself so suddenly and suspects foul play. The team investigates and discovers that the suicides are actually staged murders, caused by an "Angel of Death" type who had been attending the victims' group therapy sessions looking to "save their souls from their grief". After the catching the killer, the cop thanks the BAU for their help and for vindicating his suspicions. However, the team reveals that they had looked into his brother's suicide as well and it turns out that he had never been to the same support groups as the killer and his suicide did not match the killer's MO, meaning his death was very likely an actual suicide, something the cop is heartbroken to hear.
- Frequently done on Law & Order as well. In one episode, the detectives have found the remains of a woman believed to have died in the 9/11 attacks (her hand was found at the scene, along with her purse). The prosecutors are trying the man she was having an affair with. Serena, a woman, notes two things—that the purse in question was an evening bag, not something that a woman would be carrying for a day of work, and that her boyfriend had claimed that it was her work bag. The inconsistency reveals that he is the woman's killer. Because, apparently, no boyfriend in history has ever misidentified which purse his girlfriend uses for which occasion or failed to notice any difference at all.
- Unsolved Mysteries: A segment featured a missing woman whose husband claimed that she had walked out on him, citing that several of her things and her suitcase were missing. When her suitcase was found, it contained exactly what he said it would, peaking the cops' suspicions, as they found it highly unlikely that any man could know exactly what was in his wife's suitcase, as he himself had no idea what was in his own wife's purse. (It's actually a very sad aversion, as to this day, the woman remains missing, and despite the cops' strong suspicions that he killed her, they have zero evidence to support this, meaning he remains a free man.)
- Law & Order: UK:
- A murder suspect's alibi is that she and her girlfriend spent the day shopping and having lunch. They claim to have paid for everything with cash (to explain the lack of credit card records) and to have thrown out the receipts for their purchases. DS Ronnie Brooks scoffs at this:
Ronnie Brooks: I've been married twice. NO woman throws out the receipts for clothes she just bought!
- CP Alesha Phillips gets leery of a defendant's claim that she acted in self-defense — killing the victim after he raped her — when the girl is completely blase about having to testify, citing that most rape victims are usually terrified at the prospect, as she was.
- In another episode, a murder suspect claims to have left his job at "5 o'clock. On the button." When the detectives question his boss, DS Matt Devlin gets suspicious when the man uses the exact same phrase. While he's correct in suspecting that the two are lying and rehearsed their stories, the thought that either man could have simply picked up the phrase from the other after years of working together never occurs to him.
- A murder suspect's alibi is that she and her girlfriend spent the day shopping and having lunch. They claim to have paid for everything with cash (to explain the lack of credit card records) and to have thrown out the receipts for their purchases. DS Ronnie Brooks scoffs at this:
- Related to the above LOUK post, conversely, people having receipts that verify that they were elsewhere when a crime was committed seems to somehow indicate their guilt both for TV and real cops (as seen on numerous programs that profile real murders), most of whom say something like, "Nobody saves receipts! He/she is trying too hard to create an alibi!"
- This is cited on an episode of Forensic Files, "Yes, in Deed", where the prime suspect saving a movie ticket stub to establish an alibi was one of the reasons the police, and one of the prosecutors, believed that he was the culprit of a murder and arson. One of the detectives interviewed remarked that nobody ever keeps their movie stubs, eliminating all who might do so for any number of reasons. It was mentioned that the suspect wasn't in the habit of keeping receipts, though.
- It also comes up in an episode of Dateline, where a man suspected of killing his parents produced a receipt from a supermarket to prove he was elsewhere. Security camera footage confirmed this. However, the cops were still suspicious, as the store was very near his parents' home. Forensic evidence soon determined that he was in fact the killer and that he had gone shopping either before or afterwards to try and create an alibi.
- People having any kind of precise information regarding time — "6:36" — or place seems to make the police leery, as it apparently isn't something people usually take note of.
- Virtue's Last Reward has weird in-universe example when the clue is counterfactual to story's rules rather than real life ones. When Luna asks Sigma how he knows that Dio killed the Old Lady, Sigma replies that Dio confessed to it in another timeline. When Luna calls him out on using knowledge from different timelines Sigma replies that it doesn't matter when he found the information since events that happened in the future of different timelines cannot change the past. Except they can and it's a major plot point.
- Used in-story in Tales of the Questor, Quentyn says that some human coins are forged because the heads are facing the wrong way. He's wrong about the heads. The coins, however, really are forged and a guard sees a tradesman's look of utter horror, tipping the guard off to who's behind the forgeries.