A highly publicized crime has just been committed, with the criminals bearing distinguishing marks that make them easy for the general public to recognize if they see them out on the street. Unfortunately, those distinguishing marks are also generic enough for anyone who has similar features to be mistaken for the criminal.
Usually, when this happens, the person(s) who mistook the innocent person for the perp will overreact, and either call the cops and/or go after the suspect themselves. Or, in a similar vein, the mistaken-for-perp performs an action that, to a police officer or passers-by, seem suspicious and paramount to guilt in the crime, even though in reality the action was meant to be innocuous or even helpful to the situation. Either way, Hilarity Ensues... unless played straight, in which the victim of the mistaken identity is either beaten to death by a vengeful mob or wrongly imprisoned.
A more general superset of Mistaken for Murderer.
The trope name comes from the old saying "Guilt by association", which itself invokes the real-life charge of accessory to the crime, but is separate from Guilt by Association Gag in that someone is punished along with a group despite not actually having anything to do with the crime and is generally a comedy trope.
- Watchmen: Nite Owl is a Legacy Character. The original Nite Owl went public and wrote a book after his retirement from being a superhero. The current Nite Owl, whose identity is never publicly known, helps break Rorschach out of prison during a prison riot. A street gang wants to get revenge on him for that and they assume that the publicly-known Nite Owl is the one who did it, so they break into his house and kill him.
- In the original Teenage Mutant Ninja Turtles comics, April and the turtles once got chased by the police because April's van coincidentally was the same make, model, and color as a van used by a group of bank robbers earlier that day.
- Vigilantism was something that bothered director Fritz Lang:
- In M, the scare over the child killer is so great that one completely innocent man gets attacked by an angry mob just for speaking to a child.
- His first American film, Fury (1936) stars Spencer Tracy as an innocent man who's nearly killed by a lynch mob — but in what could be a case of He Who Fights Monsters, he attempts to frame the entire mob (or at least the 22 people shown in newsreel footage of the crime) for succeeding in his murder.
- In Master of the Flying Guillotine, the eponymous villain goes on a vendetta after a one-armed boxer killed his disciples, murdering every one-armed man he stumbles across.
- Inverted in Out Of Time. An older white woman who was a witness to a crime describes a black man to a sketch artist and then points out the chief of police (and, coincidentally, the man she saw at the crime scene) as being the culprit. After a tense pause, she starts pointing out every black man in the station which discredits her testimony, and marks one of many close calls for the protagonist while he tries to slow down the investigation that is leading straight to him.
- V for Vendetta had V send copies of his mask to virtually the entire population of London. State Sec overreacted when children started wearing them, resulting in even more of a backlash from the people against the government.
- A 1940 The Batman serial really goes over the top with this. The masked villain gets a distinctive cut on the back on his hand while getting away...and suddenly three major characters are sporting them, and the mystery of who he is is kept alive a bit longer.
- This forms the plot of the Alfred Hitchcock film The Wrong Man. Manny Balestrero, a musician at New York City's Stork Club, so resembles a man who had twice held up an insurance office that police are called when Manny unknowingly goes there on business. He is arrested after several witnesses identify him as the robber, and in providing a handwriting sample he misspells a word which was also misspelled in a note written by the robber.
- In Moms' Night Out, Alysson reports the minivan as stolen after she missed the multiple messages that Sean leaves saying that he needs to borrow it and left the other car. This leads to a car chase and Sean, Marco, and Kevin being hauled off to jail for being suspected of stealing the van, abducting the kids, and killing "Mama" (actually a parakeet).
- The Wheel of Time: After Rand announces himself as the Dragon Reborn, it's mentioned that anyone in the area who is remotely similar to his description (young, male, red hair, tall) is at risk of being attacked.
- In the Sten series, there was operation Nightfog, a purge of military personnel who'd been conspiring to bring down the Council which usurped The Empire:
There were, of course, mistakes.
A writer of children's fiche named White, much loved and respected, was unfortunate to live in the same suburb as a retired major general named Whytte. The writer's house was broken into in the middle of the night. The writer was dragged to the center of his living room and shot. The writer's wife tried to stop the killers. She was shot as well.
When the mistake was revealed, the head of the murder unit ... thought the matter an excellent joke.
- In A Song of Ice and Fire, after Tyrion is framed for poisoning Joffrey, Cersei offers a huge reward to anyone who brings her the head of her dwarf brother Tyrion, which leads to a steady stream of people bringing her the heads of innocent dwarves and the occasional child. The murders go unpunished because Cersei doesn't want anyone to hesitate if they actually do find Tyrion and aren't entirely certain of his identity.
- Tyrion's brother Jaime is guilty of a lot of things, but he's also undeservedly blamed or hated for a lot that he had no part in (The Red Wedding), or was in reality his most heroic act (killing King Aerys), mostly due to very unfortunate coincidences. Even in A Feast for Crows, where he has turned a new leaf and become one of the most honest characters in the story, these will never let him go.
- A lighthearted version features in Aunt Dimity Digs In: several people see two hooded figures in the vicinity of the vicarage the night an old pamphlet is stolen from the vicar's desk. Throw in fog, lights, and a Crop Circle, and Hilarity Ensues.
- Used seriously in The Ox Bow Incident, where a trio who just happen to have a herd of cattle from a rancher that was supposedly killed by rustlers is persecuted and hung vigilante-style by an angry mob. Upon realizing the men were innocent, the mob is naturally guilt-ridden.
- In A Series of Unfortunate Events, Jacques Snicket is jailed for having the same tattoo on his ankle that Olaf has, and just as the Boudelaires cannot convince most people that Olaf in disguise is, in fact, Olaf, they also cannot convince anyone that Jacques is, in fact, not Olaf.
- An episode of CSI involved the beating death of a taxi driver by an angry mob after he supposedly ran down a young kid. Not only was the kid already dead when the taxi rolled over him, but the driver — whom the mob assumed was getting back into the taxi to drive away — was actually reaching for his CB radio to call in the accident. Fortunately, the mob was prosecuted for it.
- Justified in an episode of Drake & Josh — Josh not only resembles the Theater Thug, he was hired to play the criminal on "America's Most Wanted". Is it any wonder people kept trying to get him arrested?
- There was a TV Show on PBS a while back about thrift stores and other ways to get cool used stuff. To start the journey, the show's hosts bought a retired ambulance on eBay to cart their findings around in. Several weeks into production, some terrorists stole an ambulance. Within a month, they had been pulled over by, interrogated by, and gotten signed statements from troopers in at least three states attesting that it was not these guys. Not that any of the troopers believed the previous ones, of course.
- In many Doctor Who stories, the Doctor arrives in an environment (e.g. research base, spaceship, space station) shortly after sinister events have begun occurring, usually including deaths. The person in charge (e.g. commander, director of research) assumes the Doctor and companion/s did it. (Admittedly, under the circumstances, that's often not so unreasonable.) Then the Doctor and companion/s are opposed by the people they're trying to help, as well as the actual villain/s.
- A fifteen year old boy (at the time) in Flashpoint was accused and sentenced for raping and murdering a classmate of his, being the last person to see her and the lawyer against him faking a witness that he had confessed to the crime, so the case could be wrapped up.
- One episode of The Mystery Files of Shelby Woo, Shelby and friends were trying to figure out who stole jewelery from a safe and became very suspicious of a magician who they spotted trying to conceal a small box on the porch. Once confronted, he began looking very guilty and his wife started to cry. Turns out he was on a diet and was sneaking food behind her back.
- In both William Shakespeare's play Julius Caesar and in reality, Cinna the Poet was murdered by a mob due to his shared name with one of Caesar's assassins. This was ironic, historically, as he was a friend and supporter of Caesar, but Shakespeare introduced some black comedy by having a member of the mob comment that even if this Cinna isn't the guilty one, being a bad poet is reason enough to kill him. This was something of a Take That Me in the original production, where Cinna the Poet was played by Shakespeare himself.
- Actually averted in Fire Emblem: Path of Radiance. Sothe gets no suspicion cast upon him by any characters, despite the group finding out there's a spy on the ship the chapter he joins.
- In The Simpsons episode "The Great Money Caper", Homer and Bart's attempt at Con Artistry ends up with them losing the family car to a fake cop. To explain their loss to Marge and Lisa, they make up a description of a fake thief. Groundskeeper Willie happens to match their description, and is fast-tracked to a guilty verdict. It turns out this is all an elaborate prank, done for unexplained reasons, though Willie wasn't in on it.
- In an episode of The Boondocks, Tom, a criminal prosecutor, is arrested for supposedly resembling the X-Box Killer.
- For a while in the 1990s & 2000s, any young person who wore a trenchcoat was more often than not accused of being part of the legendary "Trenchcoat Mafia", a presumption made famous from the (equally erroneous) accusation that the perps in the Columbine High School shootings were part of the gang (which the Trenchcoat Mafia technically were not).
- Occasionally, it's been reported that actors that work for shows like Unsolved Mysteries and America's Most Wanted have the police called on them by people who, having seen the reenactments, presume they're the criminals they're portraying.
- This happened often enough that America's Most Wanted started notifying the authorities in the area where the actors lived so that they wouldn't get arrested.
- Lets not forget the good old Paedophile witch hunts in the UK no so long ago, resulting from the publication of a sex offender list in a national newspaper. It was unfortunate for those who had similar names or addresses to the accused.
- This has been repeated of late with the "No Fly" lists in the US; people who are so dangerous they cannot be let on a plane under any circumstances, yet haven't actually done anything bad enough to warrant investigation or arrest. If you shared a name with someone on that list, flying would take on a whole new dimension of fun.
- People have also been kept from voting in certain states if their name was similar to one on a list of convicted felons. This was one of the controversies with the Florida ballots in the 2000 presidential election.
- This is supposedly why the Gunman with Three Names trope exists — to prevent people with two out of the three names of the killer from being accidentally arrested or victimised.
- Journalism students are taught to be very specific about accused criminals with generic names, adding either an address or middle initial.
- During the Beltway Sniper attacks, pretty much the only evidence the police had to go on was that a white van was seen at the crime scenes. People immediately started to report every time they saw a white van, one of the most common types of vehicle on the road. Meanwhile, the shooters actually were working out of a vehicle specially modified into a sniper's blind— but it was a blue sedan. It's probable that the resulting flood of false leads delayed the snipers' arrest.
- On September 5, 1921, Silent Films comedian Fatty Arbuckle was giving a party in a San Francisco hotel room when actress Virginia Rappe's uterus began to hemorrhage. She died four days later. Arbuckle was charged with murdering her. (It's been theorized that her uterus hemorrhaged due to several back alley abortions.) Unfortunately for Arbuckle, Mary Pickford's sister-in-law, Olive Thomas, had accidentally ingested a solution of bichloride of mercury on September 5, 1920, and died five days later. (Thomas's husband, Jack Pickford, had syphilis. Bichloride of mercury was then commonly used as a topical treatment for the sores.) The fact that Rappe fell ill on the one-year anniversary of Thomas's accidental poisoning did not go unnoticed by the Moral Guardians of the time. The scandalous deaths of Rappe, Thomas and several other silent film stars in the early 1920s were among the factors that led to the adoption of The Hays Code in the 1930s.
- Possibly the case for Joseph Lesurques, one of the men executed in the Courier de Lyon case. All those who saw the murderers before the crime noticed a blond man among them, and they could have mistaken Lesurques (also a blond) for that man. Lesurques' alibi also didn't hold up and he was friends with some of the murderers, cementing his guilt in the minds of the jurors of the time — others have begged to differ ever since his execution in 1796, but the sentence was never overturned.