One of the implications of Seers (and Time Travel) is that we can predict crimes, and so we can prevent the crimes from happening. This trope is about taking evidence from the future, and preventing the criminal from doing something they haven't done yet.
Without knowing the future, crime can only be minimized by punishing people for crimes after the fact. Precrime Arrest is when a character who is known to be going to have committed a crime is punished in advance, in order to prevent their supposed future actions. If the offender is caught early enough, they may suffer from Bewildering Punishment because they haven't even thought of committing the crime yet.
Attempts to arrest/execute Hitler are popular enough to form their own trope: Hitler's Time Travel Exemption Act. Examples of Time Travel being used for Hitler specifically belong there.
Although in Real Life methods of justice exist that produce a similar result (such as preventative detention in Europe and Asia), a setting wherein world-wide acceptance of this trope as a law enforcement tool exists is a pretty heavy example of Hollywood Law and Artistic License Law. To make a long story short, many laws that exist today have (theoretically) a heavy emphasis on "innocent until proven guilty" and "punishment after the crime". If the possibility—even if incredibly small—exists to Screw Destiny, then the usage of this Trope could probably be seen as unfair arrest or (in the most extreme examples when people do nothing but wait until the event happens and taking action Just in Time) entrapment. And this is without going into the mind-bending details of arguing how the Timey-Wimey Ball is in effect, too...
- Psycho-Pass takes place in the year 2112. Japan is governed by the Sibyl System, which measures many psychological factors. One of the things determined by scanning people is the "Psycho Pass", or the mental stability of a citizen. The colour of a Psycho-Pass is then used to measure the "Crime Coefficient," the probability and severity of the crimes a person might commit. Those who have a high enough "Psycho Pass" are sent to psychiatric therapy or completely euthanized by Dominators, a type of gun used by the police. People who have a high "Psycho Pass", but haven't committed any crimes, are called "latent criminals". They generally have two choices: Rehabilitation, or become an Enforcer for the police.
- Dragon Ball Super plays with this. Beerus executes Zamasu partly for his various crimes, the bulk of which he has yet to commit, while avoiding the legal problems outlined above due to knowing with certainty that he is going to do it. And because it's not like the letter of the law matters to a God of Destruction.
- In Heat Guy J, this is the theoretical purpose of the Special Unit, and why they are allowed to use an android even though androids are illegal within the limits of the city-state. However, in practice, they don't end up making too many arrests before any sort of crime is committed.
- In Swordquest, the Big Bad Tyrannus orders the infants Torr and Tarra to be killed simply because his Evil Sorcerer prophesied his death at the hands of blonde-haired twins.
- Civil War II: Captain Marvel wants to use a new character's powers to stop crimes and attacks from happening. She faces opposition in the form of Iron Man and his allies who refuse to punish people before the crime. Things become a whole lot more muddied when Tony Stark presents evidence that the visions are not one hundred percent accurate to begin with- based more around the subject 'doing the math' to calculate the odds of certain things happening rather than definitively seeing what will happen- and factors like Ulysses (the seer) having some kind of prejudice can make them even more inaccurate but Carol Danvers absolutely refuses to hear it. And then it turns out that one of the people Carol arrested because the visions saw her commit a terrorist act decides to become one when Carol lets her go in the arc's epilogue out of sheer hatred for Captain Marvel — although so far nothing has come from it.
- Judge Dredd:
- Judge Death and his fellow Dark Judges have a rather psychotic take on this: since all crimes are committed by living people, the only way to get rid of crime is by killing everyone in existence. They believe that life itself is a crime punishable by death.
- Justice Department runs a trial program where Psi-Division predicts crimes and the perp is sentenced before the crime occurs. Unfortunately, the one guy they do arrest for a murder yet to happen ends up committing the crime anyway as a direct result of his arrest. Dredd notes that there's a flaw in the idea somewhere.
- The Angel comic has an interesting case; in the first arc, Los Angeles is dragged into Hell; and at the end of the arc, the Reset Button is pushed, returning all Angelinos to Earth alive and well as if no time had passed. However, the following arc deals with a group of apparent real angels killing what seems to be random people. Angel tracks them down, and discovers the killings aren't random at all; the victims had been up to seriously nasty shit while LA was in Hell, and even if those actions were undone, the angels don't really see any reason to forgive them. Angel, desperate to come up with a utilitarian argument against precrime execution, persuades them it's possible that these people might end up doing so much good in their subsequent efforts to atone to outweigh the evil they did in Hell. This was supposed to be explored further over the next few arcs — A repeated theme of the TV series is that attempting to "balance the scales" is doomed to failure because future good deeds can never really make up for evil acts, so one must do good in spite of them, not for some vague "redemption"; meaning that there are a lot of people in LA who have to accept their capacity for evil and decide what to do next — but as soon as a new writer took over, the "angels" were retconned as having been evil demons from the beginning anyway, rendering the whole arc moot.
- An issue of Savage Dragon deconstructs this when an alien (that had landed on Earth some years before and was raised by some kind farmers) starts attacking people seemingly at random and kill them. The characters theorize that the alien has a capacity to see the future and the alien's "father" believes that the people who were killed would have become violent criminals in the time to come, and thus the alien was taking them out pre-emptively to avoid mass murders. The deconstruction is that, as Dragon points out, there is no real evidence of this being true (the alien is pretty inscrutable, for one)... and the fact that people have died before they would ever commit any kind of crime means that there never will be. Which means that the alien is (in the eyes of the law that Dragon has sworn to enforce) nothing more than a homicidal maniac that needs be stopped now.
- In the Silver Age, the Legion of Super-Heroes once incarcerated Superboy in a kryptonite prison, after they had witnessed him committing several acts of wanton destruction through a "futurescope" and concluded that he would become a supervillain in the future. In the end, it turned out that Super Dickery was in full effect as he was actually destroying an extremely dangerous weapon and things connected to it (which the Legion didn't know about, because everything had been covered up by the government).
- In Minority Report, the Trope Namer, three psychics are used by the state in order to apprehend and subdue people before they commit murder, keeping said latent criminals into a vegetative state. There is talk of expanding it into lesser crimes, as well, although the As You Know conversation at the beginning explains that only murder is strong enough to trigger a psychic vision. During the "Precrime experiment", the captured criminals are detained in a comatose state with electronic files on their future crime. When the movie ends with the protagonist proving that people don't have to commit the crime they are predicted to commit, the criminals are released because he proved there was enough reasonable doubt to overturn their convictions.
- In Captain America: The Winter Soldier, SHIELD's Project: Insight is based around having three all-new Helicarriers designed to police the world, taking out potential threats before they do any actual threatening. In truth, the project is under the control of HYDRA, and the Insight Helicarriers are driven by an algorithm designed by Arnim Zola to calculate any and all potential threats to HYDRA's World Domination, and terminate them all.
Col. Nick Fury: We're gonna neutralize a lot of threats before they even happen.
Cpt. America: I thought the punishment usually came after the crime.
- In Prince of Persia: The Sands of Time, by the end, Dastan is propelled back to when he first caught the Dagger of Time. Already knowing his Evil Uncle's plot, he tries to prevent it from happening. And is successful.
- Terminator 2: Judgment Day. Sarah Connor learns from the Terminator (who time traveled back in time to her present day) that the person most directly responsible for the creation of Skynet is a Cyberdyne Systems engineer named Miles Dyson. She tries to assassinate Dyson to prevent Skynet from ever existing. Notably she can't bring herself to finish him off, instead collapsing into tears when she realizes she's about to kill a husband and father who hasn't actually done anything wrong.
- The 1996 B-Movie Past Perfect involved a justice program from 20 Minutes into the Future that sentenced criminals and then sent hunter teams back in time to kill them just when they were starting their careers. While most of them are irredeemable jackasses, one of them (who was the gang's rookie and had not yet crossed the Moral Event Horizon) ends up declaring that he wishes to repent and his criminal record changes because of the Butterfly of Doom—still, this is not enough for the team's psychotic leader and he continues trying to kill the kid. The film's epilogue shows that the cop that was the protagonist, now a judge, started the program in the future... but the events of the film had him change it to send people back who could teach criminals how to take a better path before they became irredeemable.
- Isaac Asimov's All the Troubles of the World: Multivac's precrime functions alert the police to crimes before they happen. They then intervene by warning and detain only in rare circumstances. The ability has been expanded several times over, and the next stage is anticipating outbreaks of illness. But the plot kicks off when the arrest of an accused criminal increases the crime's probability of execution. The police are scrambling to figure out how to stop a crime worse than murder. The twist is quite the whammer: the whole story occurs because Multivac has manipulated things so someone would be driven to try to wreck the machine, with its direct (secret) help. That particular person is stopped Just in Time, but the last line of the story is Multivac telling its creator: "I want to die".
- The Minority Report by Philip K. Dick is the Trope Codifier, featuring "Precrime" as the name of a criminal justice agency, whose task is to identify and eliminate persons who will commit crimes in the future. The film Minority Report is based on this story.
- In Through the Looking-Glass, the White Queen tells Alice that the King's Messenger (the Hatter, or 'Hatta', by the illustrations) is in prison for a crime he has not yet committed, or been tried for. (This is Looking-Glass Land, which is in some ways time-reversed.)
- Doctor Who: "Let's Kill Hitler" features the obvious Hitler's Time Travel Exemption Act, from Melody Pond and from new character/crew Justice Department Vehicle #6018. The Justice vehicle is sent to painfully kill time's greatest criminals just before their death (and after their crimes). They realize they've arrived too soon in Hitler's personal timeline, and find a bigger fish: The woman who killed the Doctor. Except that she hadn't done that yet, either.
- One episode of Hercules: The Legendary Journeys had Iolaus given a chance by Dahak to save the life of a man who was hanging precariously from a rope bridge. However, Dahak also showed Iolaus that if the man survived, he would soon go on to rob and kill an innocent family. Iolaus chose not to save him and let the guy fall to his death. Dahak then gleefully pointed out that since the guy had not actually committed a crime yet, Iolaus technically murdered an innocent man, conveniently ignoring the difference between actually killing someone and not saving him from something else.
- Minority Report (2015): It has been eleven years since the end of the Pre-Crime experiment, where people were arrested because the precogs saw them commit murder in the future. Now, Peter van Eyck wants to develop a new system of crime arrest based on computers and data analysis rather than "genetic freaks" in order to accomplish the same thing. The precog Dash joins with Detective Lara to prevent the murders Dash predicts.
- The Outer Limits (1995): In "A Stitch in Time", a professor who was raped as a teenager invents a time machine, using it to go back in time and kill serial killers before they could claim any victims. She even limits herself to killers who have not only been convicted but executed for their murders, but since all her victims hadn't killed anyone yet, law enforcement sees them as completely innocent victims of another serial killer with a career spanning forty years. She eventually undoes her own motivation to do this by rescuing her teenage self, but still invents the time machine because she clearly remembers her future self stepping through a time portal. So as one of her victims went on to kill the partner of an FBI agent — a murder originally undone though time travel, then re-done by the rescue — the agent goes back to save her partner by killing the killer. It's implied that the agent will go on a similar time-travelling killing spree to the one she spent the episode investigating.
"Our yesterdays are like a string of pearls — unbroken — unchanging. But if we could change our past, would that also change who we are?"
- Person of Interest centers around preventing premeditated violent crimes before they happen through the predictions of a sentient supercomputer. Since the predictions are generally made some time between the end of the planning phase and the beginning of the execution phase of the future crime, there's generally enough evidence to turn them over to the police for attempted murder. The problem arises because the existence of the Machine is both illegal and highly-classified — the US government uses it to predict terrorist attacks but ignores 'ordinary' crime.
- The final season of Elementary features a similar example to the Machine in Person of Interest, but presented in a more negative manner; Odin Reichenbach is a tech mogul whose public media platforms have given him access to a range of online material that he believes can be used to anticipate future crimes. However, he is soon shown to be far too willing to take action based on that evidence while ignoring such variables as the human need to vent; as an example, Sherlock notes that he killed a school bus driver who was discussing her thoughts of killing her passengers, but a look at this womans past online history showed that she made similar rants in the past and never followed through with her threats.
- The Player centers around the people who created the system deliberately abusing the hell out of it; back in The Gilded Age, the world's first millionaires were looking for a game of chance so dangerous and high-stakes none of their lessers could ever even dream of playing it - they chose the nascent phenomenon of organized crime. Thomas Edison then used the lost journals of Ada Lovelace and Charles Babbage to develop a system to calculate the odds of crimes - and ended up with one capable of predicting all of them hours or days in advance. The Gamblers used it to place bets on which criminals would get away, but quickly discovered just about all of them did. So they started funding a Vigilante Man dubbed "The Player" and betting on whether or not he would succeed or fail in stopping criminals... or just be killed by them. They go through them quickly.
- Power Rangers Ninja Storm: In a three-part episode, Cam goes to the past to seek a power that'll make him the Sixth Ranger. Upon finding out his soon-to-be-exiled Evil Uncle is Lothor's past self, he tries to persuade the other ninjas to kill him instead. Unfortunately, they refuse to deliver punishment for future actions.
- 7Days occasionally had Frank preventing a crime as the episode's plot. Every episode, Frank is sent back in time seven days to prevent whatever disaster has happened. Sometimes he's able to do it by preventing the perpetrator from attempting the crime. Most episodes, however, this trope is subverted, and Frank has to stop the crime/disaster as it happens instead of preventing it from being attempted.
- During episode "Obsession" of Sliders, the main characters travel to a world where ten percent of the population have Psychic Powers. Amoung the various powers, is precognition.
- A bit of research into the history of this world reveals that psychics became popular when one warned Abraham Lincoln about his impending assassination, allowing Booth to be captured before the attempt.
- The Police Oracle identifies Arturo and Rembrandt as people who will kill Wade Wells, so the police make a Preventative Arrest. A Bewildering Punishment to all four at first. Basically, they're taken to the station, booked, and then released. If someone were to actually commit the crime, the police would have to chase them down, but otherwise the two are free to do whatever they want. This is all a Batman Gambit by the old Prime Oracle to make sure his successor is a compassionate man in addition to already being a powerful one.
- Star Trek: Voyager had an episode named "Relativity", where the 29th century timeship Relativity is attempting to stop a time-paradox sabotage attempt on the 24th century spaceship Voyager. After the culprit responsible for the mess is found, two earlier versions of the culprit are arrested. The Captain assures Captain Janeway that the three would be "integrated" into one person before his trial.
- Discussed but eventually averted on Crime Traveller: because of the way the rules of time travel work on the series, it is impossible to stop a crime before it happens (when it's tried, "You Already Changed the Past" instead ensues), so all that can be done is witness the event and circumstances before and immediately after and obtain clues that were not immediately apparent in the "present".
- Legacy of Kain has an example of how spectacularly bad attempting this trope can go. Throughout the first game, the land of Nosgoth is suffering under the iron hand of the Evil Overlord known only as The Nemesis. Near the end of the game, Kain finds himself decades in the past, with the Nemesis at his mercy and he kills the tyrant before his tyranny can begin. When he returns to the future, he discovers that history has recorded the murder of King William the Just at the hands of a vampire, and embarked on a campaign of genocide - a successful one, as he arrives just as the second-to-last vampire is executed, leaving Kain the last of his kind.
- This is how The Legend of Zelda's "Child Timeline" comes about. At the end of Ocarina of Time, Link is sent back in time permanently in order to properly live out his childhood. After placing the Master Sword back in its pedestal, he goes to warn Zelda and the rest of Hyrule's decision-makers about what Ganondorf is planning. This results in the passage to the Sacred Realm never being opened, while Ganondorf is sealed in the Twilight Realm instead, setting the stage for Twilight Princess.
- The plot of Watch_Dogs 2 is kicked off by Marcus Holloway, who breaks into a CTOS server farm to erase the digital files Blume has on him. His digital file contains his legal record, which stated that he was the prime suspect in a burglary, that he's a skilled programmer, and has a license to own a gun. Although there was no concrete evidence that he was responsible for the robbery, he was convicted only because CTOS calculated that he was threat because of the afromentioned variables.
- Futurama parodied Minority Report in an episode where Fry joined the police's Future Crimes division.
- The Simpsons: In the "Revenge of the Geeks" segment of "Revenge Is a Dish Best Served Three Times", Milhouse goes on a Roaring Rampage of Revenge against students who wronged him in the past. When he's about to humiliate a kid, who says today is their first day at the school, Milhouse says the kid will do something bad to him in the future, so he's still going to need revenge. ("It's called pre-venge!")
- Codename: Kids Next Door: One episode that had Numbuh 3 take on Numbuh 2's Film Noir identity features a "pre-delinquency unit" that gives Gallagher Elementary School students detentions for future rule-breaking, formed around a student seer who makes drawings out of crayons of said crimes. Turns out their seer was actually a hoax, being just a boy with heterocromia. His entire motivation was to get everyone of the kids in trouble in order to be the first in line for pizza bagels, since they'd usually run around when he arrived. Unfortunately for him, he did his scheme on a day where they were serving lima bean sandwiches.
- While in the West, outright arrest is not allowed, there had been examples, such as Chicago, of the use of an algorithm to predict its inhabitants potential involvement with violent crime, which creates a Strategic Subject List - known colloquially as the heat list - a comprehensive list of who it considers to be the most dangerous people in the city, and people are commonly warned due to this list. The reason why outright arrest is not allow is that modern Western legal systems have a heavy emphasis on "innocent until proven guilty" and "punishment after the crime". If the possibility—even if incredibly small—exists to Screw Destiny, then the usage of this Trope in real life would probably be seen as unfair arrest or (in the most extreme examples when people do nothing but wait until the event happens and taking action Just in Time) entrapment.
- While in the West it is seen as a pretty heavy example of Hollywood Law and Artistic License Law, this is already implemented by China as "Integrated Joint Operations Platform", using Big Data to identify and pre-emptively detain potential troublemakers in Xinjian.
- Preventative detention of terrorists and also criminals in general has been criticized as being this. Some countries like Germany and France allow convicts to be detained once the sentence has been served if they're deemed a high risk of recidivism.
- On a more mundane level, nearly every country has laws against conspiracy to commit a crime and in many jurisdictions you can be arrested for possessing "burglary tools" such as lockpicks unless you can prove you had them for a lawful purpose. To be charged with a conspiracy, the participants must have committed at least one "overt act" in furtherance of it however (such as obtaining guns to commit a bank robbery before it takes place).