The introduction of a key witness at the climax of a trial. Particularly one who renders everything that has gone before moot or one who would have rendered the whole trial unnecessary from the beginning because their testimony clearly absolves the defendant, or more rarely, proves his or her guilt, depending on whether we're rooting for the defense or the prosecution.
If this takes the form of physical evidence, it's a Smoking Gun.
Note: While the government may notify the defendant of witnesses and evidence on very short notice, in civil cases surprise witnesses are highly unusual, unlikely, and disfavored. Of course, the open discovery practice in civil litigation makes horrible drama.
- Turnabout Storm has one of these, which should come as no surprise considering one of the series involved is Ace Attorney. Fluttershy abruptly shows up after the defendant, Rainbow Dash, had already been declared guilty. Nevertheless, she was allowed to testify, and her testimony allows Phoenix to bring a key character to the stand.
- Dahlia Hawthorne Escaps From Pirson naturally has these, being an Ace Attorney fanfic.
- In the 4th chapter, we see the victim's spirit get channelled, so that she can testify, and prosecute. Later on, we even see the defendant appear as a surprise witness to his own trial, where he proves that the person on trial is an imposter.
- The 6th chapter uses the trial system of the Layton crossover, which naturally lends itself to this trope. Oldbag shows up to reveal another crime by the defendant. Then Franziska arrives to add a bit of extra testimony in relation to the identity theft from the 4th chapter, putting the final nail in the coffin.
- In My Cousin Vinny the District Attorney introduces a surprise witness, an FBI analyst. Vinny, having studied very hard to make up for his inexperience, points out that the prosecution in US criminal cases is not permitted to introduce a surprise witness, therefore he should be permitted time to investigate the witness (the judge applauds his erudite and well-reasoned objection, then overrules it, allowing the witness to testify). However, the real surprise witness of the movie is his fiancee, who proves that the car driven by the defendants couldn't have made the tire tracks of the murderers' car.
- Subverted in A Few Good Men when Kafee points out two airmen who he implies would prove that part of Jessep's testimony was a lie. After he pulls a Perry Mason and gets Jessup into a Motive Rant, he admits to the prosecutor that it was a con, and the "surprise witnesses" wouldn't have been able to prove a thing.
- The climax of the trial in Anatomy of a Murder occurs when the defense attorney, after a moment's leave of absence, returns bringing in Mary Pilant, who had earlier disbelieved that the defendant's wife had been raped by the victim but now realizes the significance of a torn pair of panties she had found in the laundry chute. She's a more realistic version of the trope, as she had previously been called to testify to other aspects of the case, and would therefore have already been subject to the discovery process.
- In the court scene of the The Kentucky Fried Movie the prosecution produces a surprise witness - a woman thought killed in the incident the trial is about. She gets on the stand and fingers the person responsible for the incident - the reporter covering the trial.
- The Verdict: Galvin spends a good portion of the film trying to hunt down an admissions nurse for his ongoing medical malpractice case. When he finally tracks her down, he calls her as a rebuttal witness, which allows him to call her without notifying the defense. However, her status as a rebuttal witness ultimately helps the defense throw out her testimony on a legal technicality.
- In the Star Wars Legends novel The Krytos Trap, a well-known X-Wing pilot was put on trial a few years after Return of the Jedi for the murder of a squadmate and turning traitor to the government. At the end of the trial, with a guilty verdict hanging over his head, the "dead" squadmate walks right in and blows the prosecution out of the water in all of five minutes, coincidentally having picked up the proof that the pilot wasn't a traitor (and having figured out the identity of the real traitor as a result) on his way back from the dead.
- In fact, that was the second surprise witness, after an Imperial agent defects with proof that the defendant is innocent but is shot before reaching the courthouse. Both are handled as realistically as possible under the circumstances: the defense does properly report the first new witness as soon as they know about it (rather than springing the surprise in the courtroom as is usual for the trope), and the second witness is a surprise to everyone except for one R2 unit who is there—and it's less a case of withholding information and more a case of the interpreting 3PO unit not believing the R2 unit. (Which, under the circumstances, is quite understandable; the person in question is supposed to be dead.)
- Mrs Figg in Harry Potter and the Order of the Phoenix.
- Totally and almost sadistically subverted in The Brothers Karamazov. During the trial, a sick and borderline insane Ivan tries to save his elder brother Mitya by revealing who the real murderer is, but a)No-one believes him, b)He finally snaps and loses his grip on reality, and c)His testimony prompts another witness to produce an apparently incriminating clue against Mitya, pretty much hammering the last nail in the coffin of the case.
- In Dan Abnett's Warhammer 40,000 Gaunt's Ghosts novel The Guns of Tanith, Commissar Viktor Hark intervenes in the trial of Trooper Caffran at the last minute, bringing in a surprise witness who absolves him of the rape/murder he's being charged for. Colonel-Commissar Gaunt then correctly deduces that the witness in question was a false witness Hark had prepared specifically to get Caffran off the hook to keep morale up in the regiment.
- Gaunt himself then has to dredge up evidence to prove that there is reasonable doubt in the case of the person who actually did commit the crime in order to get him off and prevent a split in the regiment.
- Miles Vorkosigan is a Surprise Witness at his own trial (it's complicated) in Lois McMaster Bujold's The Warrior's Apprentice.
- In Dorothy L. Sayers' Clouds of Witness, they are prepared to produce a Surprise Witness. Unfortunately, since it's an alibi by a woman he was having an affair with, it would be embarrassing all around, dangerous to the woman, whose husband is jealous, and prove the prosecution with a motive, since if the dead man knew it would be reason to silence him. Fortunately, Lord Peter Wimsey manages to produce a Smoking Gun instead.
- The entire premise of Agatha Christie's Witness for the Prosecution, later turned into a play & a film.
- In Irving Wallace's The Seven Minutes a publisher has been taken to trial for publishing a book (of the same name) which is allegedly pornographic. The trial revolves around whether the absent author (believed by hearsay to be dead, and insane when he wrote it) intended the book as a work of pornography or as a work of art. The prosecution favours the former, but is utterly torpedoed when a prominent witness for the defence turns out to be the author (who had published the book under a pseudonym). In this case, it is the identity and not the actual presence of the witness which is the surprise.
- In McAuslan's Court Martial, the defence hinges on the surprise testimony of Regimental Sergeant-Major Macintosh, who in response to carefully exact questioning informs the court that (i) he, the RSM, is a former Sergeant Major in the Scots Guards and therefore probably one of the ten smartest and most expert parade-ground soldiers in the entire British Army (ii) he has carefully trained the soldiers of his current regiment to the point that they will compare favourably to anyone except the Guards (iii) the regiment recently provided an honour guard for Edinburgh Castle, no less, at which event the need for smartness is a foregone conclusion, and (iv) at that event, the defendant Private John McAuslan, whose legendary dirtiness is a key plank of the prosecution case, was a member of the six-man guard detail. He then majestically rises and exits the courtroom before the stunned prosecutor thinks to cross-examine him and reveal (v) owing to bizarre circumstances that could make the regiment a laughing-stock, they drafted in McAuslan on that occasion not because his presence could be viewed as in any way desirable but because there was literally no-one else available.
- Used repeatedly in the Rumpole of the Bailey books (and the TV series that preceded them). Rumpole's case frequently relies on the testimony of some last minute witness that he just happens to have bumped into in a completely unrelated situation. The judge and/or prosecutor always allow the surprise witness after some grumbling, often because another unrelated incident has given Rumpole some embarrassing information that he can use to blackmail them.
- Error Of Judgment: A resident who (like Craig) exposed Prince at his last hospital is found and brought before the board of inquiry just as they were about to render a judgment in Prince's favor, and fire Craig.
- Divorce Court: The 1950s and 1980s incarnations — the ones which featured fictionalized productions based on real cases — had the surprise witness as its bread and butter. Often, the trope came into play when one of the litigants is clearly winning and about to bury his/her soon-to-be ex-spouse in court. The witness would always bring evidence that would seriously damage and ultimately discredit the winning litigant and swing the case in favor of the more sympathetic litigant. (Example: The defendant in a case where physical cruelty and adultery are among the issues has seemingly disproven his wife's claims as rantings of a mentally ill woman ... when all of a sudden the doors fly open and the man's ex-wife (deciding she needed to testify rather than be intimidated into silence) barges in and tells how she was abused by the defendant.)
- Superior Court and The Judge: See Divorce Court for trope usage in these late 1980s courtroom dramas.
- These occasionally annoy the cast of Shark.
- Often in Law & Order, the mere threat of a surprise witness (even one who had a 50/50 chance of being kept from the stand) is enough to force a guilty plea.
- In Battlestar Galactica, Romo Lampkin puts his "associate," Lee Adama, on the stand during the trial of Gaius Baltar, ostensibly as part of his motion for a mistrial; Lee had heard his father, one of the judges on the tribunal, call Baltar a "traitor" unworthy of a trial. However, Lee decides that he can go too far in his little war against his father, and refuses to directly testify about his father's statement. This still leaves the door open for Lampkin to ask other questions, resulting in a speech on the part of Lee that resulted in Baltar's acquittal. Probably justified by the fact that Lampkin was the only one who knew anything about law in the courtroom, and more than happy to fudge the rules a little.
Judge: This is highly unusual—Lampkin: I can list half a dozen precedents off the top of my head.
- Parodied in Monty Python's Flying Circus episode 3 (along with several other Courtroom Antics), in which a barrister first calls a Mrs. Fiona Lewis, who babbles incessantly and incoherently. This is followed by "the late Arthur Aldridge", who is in a coffin (and may or may not be dead), and then Cardinal Richelieu (as a character witness), who upon cross-examination is quickly exposed as a professional impersonator based on the obvious fact that Cardinal Richelieu has been dead for over 400 years.
- Heroes episode "Pass/Fail":
Ando Masahashi: The defense calls Hiro Nakamura to the stand.
Hiro Nakamura: Don't you watch Law & Order? That always backfires!
- The French and Saunders sketch in which their backing band, Roland Rivron and Simon Brint, imagine suing Ralph McTell for publishing an "easy" guitar book without those little diagrams that show you where to put your fingers on the fretboard. Their surprise witnesses are Mark Knopfler, Lemmy, David Gilmour, Mark King, and Gary Moore; all of whom are utterly unable to play their own signature pieces based on the book.
Rivron: I'd like to call to the stand another very surprising witness...
- Touched by an Angel episode "Smoke Screen" has a tobacco company as a defendant of a class action lawsuit. Opposing counsel, Marc Hamilton, has to deal with a surprise witness near the end of the trial - his own mother. The court only acknowledges the conflict of interest by asking the plaintiff's council if she objects to Marc cross-examining his own mother, instead of dismissing the defendant for a conflict of interest. When Marc asks for a recess to consider what's going on, the court only states that he is "running out of recesses".
- During the last season of The Facts of Life, Blair went to law school. Her first court case was a murder trial where she later realized that the "victim" was only faking her death to frame the defendant. Her solution: have Tootie show up disguised as the "victim" and appear to go deliver a testimony to prompt her co-conspirator to say something stupid. It works. Then, it's revealed that Tootie was unable to make it and is not the woman in disguise. After a few confusing seconds, the woman reveals herself to be Beverly.
- Better Call Saul has Jimmy using Huell as a surprise witness. However Jimmy did write his name in the list of witnesses, he just didn't elaborate what his testimony would be about. Huell planted a battery on Jimmy's electro-sensitive brother Chuck for almost an hour and Chuck felt nothing, proving that Chuck's sickness is mental despite what he claims and cause him to blow his whole case against Jimmy in a rant.
- The Wall: Mother in "The Trial" definitely comes across as one—she dive-bombs into the courtroom.
- It's very rare for one of these not to bedevil an Ace Attorney case at some point.
- One particular case has the witness show up after the guilty verdict had already been handed down, and their testimony blows the entire case wide open. Manfred von Karma doesn't believe in surprise witnesses (since he coaches everyone he puts on the stand to make his case airtight). That's why when Larry shows up it throws off his game so much.
- Professor Layton vs. Ace Attorney:
- Emeer Punchenbaug manages to be the surprise witness in two separate unrelated cases. He also manages to be a surprise witness in a case he already testified in!
- The final trial has the final surprise witness be the supposed murder victim himself.
- Phoenix Wright: Ace Attorney Spirit of Justice:
- In the 3rd case, the victim's spirit is channelled so that he can testify.
- In the 4th case, Athena finds evidence pointing to someone named Owen. She makes it her mission to bring this person to the stand, even though no one seems to have heard of anyone by that name. (The witness currently on the stand has Dissociative Identity Disorder and one of his alters is Owen) Sure enough, this person's testimony blows the whole case wide open.
- If you give Marcus Bishop's dagger at the end of act 1 of Neverwinter Nights 2, he becomes one in your defense during the trial in act 2.
- The Simpsons: Like the Star Wars example, the "deceased" Skinner barges into the courtroom to clear Bart's name.
- In another episode Lionel Hutz promised Homer "surprise witnesses, each more surprising than the last. I tell ya, the judge won't know what hit him."
- In yet another Hutz stalls for time and brings out all his surprise witnesses again. The crowd groans, and we see that the witnesses are a man with a dummy, Santa Claus with a broken leg on crutches, John Swartzwelder (Simpsons writer), Ralph Wiggum and the McCrary twins on their motorcycles.
- In yet another another episode, Bart *is* the surprise witness as only he could clear Mayor Quimby's nephew, but he would have to admit to cutting class to do so. The judge even lampshades this: "Although re-opening a trial at this point is illegal and grossly unconstitutional, I just can't say no to kids."
- Family Guy:
- Though not actually called as a witness, Peter is on trial for murdering Lois, and is about to be found guilty, when the trial is interrupted — by Lois.
- In another episode, Peter called out "The Ghost Who Never Lies" to testify on his behalf, and claimed only he could hear or see it. The judge allowed it. And the ghost accused Peter.
- Subverted in the Trial episode of Avatar: The Last Airbender. When Aang is accused by a small town of murdering their king in a past life, Sokka and Katara gather large amounts of evidence to prove his innocence, but they mean nothing in this town's Kangaroo Court. In the end, Katara attempts to get Avatar Kyoshi to manifest herself through Aang in the hope that she will prove the Avatar's innocence towards the murder of their king. Kyoshi did appear, but...
Aang: What happened?
Katara: Uhh, you kind of confessed. Sorry.
- Justice League Unlimited: John Stewart, the Green Lantern of that League's incarnation, was accused of blowing up a planet and killing its inhabitants. While the rest of the League investigated, the Flash was left behind to stall the trial. (The Irony wasn't lost on him) Flash then introduced Kilowag (another Lantern) as a "surprise witness". When asked which sort of witness he was, Flash came with a joke about Kilowag's size.
- In an episode of Gargoyles, Goliath is on trial in a human court for knocking over a jewelry store. He finds the real killer and arranges an Engineered Tape-Recorded Confession, then brings it to court at the last minute. The trope is lampshaded by Goliath, who says that he knows it's not being admitted according to "your rules," but that he knows that the judge is trying to be fair. He gets off.
- Played for laughs on King of the Hill, when Hank has to convince a fraud board that he wasn't faking a workplace injury to get workers' compensation (he wasn't, of course - Hank loves work and truly loathes taking workers' comp). When Hank dramatically announces that he's calling a surprise witness, the members of the board visibly perk up, and the chairman is absolutely delighted - their job is ungodly boring, and they never get to do any fun legal stuff. A surprise witness represents a wonderful change of pace.
- In the 2015 Free Comic Book Day Atomic Robo update, Dr Dinosaur attempts to call a surprise witness who is absolutely not a genetically engineered super monster. Robo's lawyer objects on grounds that the defence is supposed to be appraised of all witnesses, and the judge tells Dr Dinosaur that he is to follow proper procedure or be held in contempt. Then it turns out the surprise witness is a genetically engineered super monster after all.
- During the trial against the creators of The Pirate Bay, the prosecution pulled in a surprise witness... and was chewed out by the court and the press for trying to pull "some kind of Perry Mason crap", which in some countries and states is illegal for the prosecution to do.