Say prosecution has a witness who saw the defendant do the crime and is happy to testify it on the stand.

But when they take the stand, they suddenly surprise the prosecution by saying they did not see anything (thereby effectively commiting perjury). They may do it because the defendant has threatened them, or offered money, or whatever. A famous (though not real) example is Frank Pentangeli suddenly saying at the trial that he knows nothing about Michael Corleone's family (crime organization) in The Godfather Part II:

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In modern criminal courts, what can the prosecution do to fix that? Can they ask the court to adjourn the trial, talk some sense into the witness and have them on the stand again to tell the truth? If so, can the prosecution just carry on with other witnesses and simply bring the liar on the stand again another day, or does it necessarily need to advise the court immediately of what has happened and request an adjournment?

  • isn't that why you have a deposition of the witness first?!
    – Trish
    Commented Dec 6, 2020 at 12:47
  • @Trish That may be an answer. I don't know.
    – Greendrake
    Commented Dec 6, 2020 at 13:59
  • 1
    Presumably they could find out if the sudden change was due to threats. At which point they can discuss witness protection in return for testimony about the threats. Commented Dec 6, 2020 at 18:43
  • The outcome would probably be different in the U.S. (which has very strong double jeopardy protections) from other common law jurisdictions (which have more exceptions).
    – ohwilleke
    Commented Dec 6, 2020 at 20:18
  • @Trish depositions aren't very common in criminal practice when the witness has already provided a statement (not necessarily recorded or in writing) to law enforcement and there is no reason in advance to suspect a change in story.
    – ohwilleke
    Commented Dec 6, 2020 at 20:19

1 Answer 1


In U.S. practice, double jeopardy protections attach once the jury is seated and this scenario contemplates the change in position arising at trial.

A mistrial could be called, or a continuance obtained, if the defendant suddenly claimed an alibi defense, since that amounts of a defendant waiver of double jeopardy protections. But without proof that the witness was tampered with, obtained at the last moment, it can be difficult or impossible to get proof of tampering or to contradict the story with other evidence to undermine the credibility of the witness.

The prosecution would probably request a recess in the trial to regroup and try to admit evidence that the testimony changing witness made a prior inconsistent statement to impeach the testimony of that witness, from whomever that witness told the first time (probably a law enforcement officer). But this is still far less convincing to a jury than an affirmative statement from a witnesses about a key fact.

If the prosecution could find evidence of defense side tampering and present it to the judge in the hours or small number of days before the trial ends, it might be able to get a mistrial declared. But it is much harder to get a mistrial for witness tampering when the witness shows up and testifies contrary to prosecution expectations than it is when the witness is, for example, killed or kidnapped and doesn't appear to testify at trial at all.

But if evidence of neither type could be obtained before the jury was sent to deliberate and evidence was closed, and the jury then acquitted the defendant, it would be very hard for the prosecution to change this result. Perhaps not completely impossible, but very nearly so.

The witness could be (and in this circumstance, despite the extreme rarity of perjury prosecutions, probably would be) prosecuted for perjury, but that wouldn't change the acquittal.

If a link to the defendant could be found, the defendant could also be prosecuted for witness tampering or obstruction of justice or something similar. But that is hard to prove (and the witness would probably have to be convicted or provided with use immunity for his testimony) to do so.

In English criminal law practice, in contrast, the likelihood of having the verdict of acquittal set aside and getting a new trial would be much greater (and the likelihood of getting a recess mid-trial would be greater in far more common bench trials in lower level criminal cases), but it would still be a serious burden for the prosecution that it might not be able to overcome.

Lawyers aren't entitled to expect that witnesses will testify exactly the way that they discussed things with the lawyers before trial, and this can be explained away with a variety of excuses that are usually true ("after thinking it over after meeting with you, I realized that I was confused and getting it wrong"), but are sometimes a cover for a change of story that is not sincere.

I've had similar things happen a few times in civil litigation and there is only so much you can do about it.

  • "regroup and try to admit evidence that the testimony changing witness made a prior inconsistent statement to impeach the testimony of that witness" the previous statement would not have been made under oath. It would have been just an interview. Would that therefore ever have any weight against what they say on the stand?
    – Greendrake
    Commented Dec 6, 2020 at 23:22
  • @Greendrake Sure. Nobody, least of all jurors, believe that people are more likely to be truthful testifying on the stand in court under oath than they are in an interview out of court. It is a legal fiction. The opposite is almost always true.
    – ohwilleke
    Commented Dec 7, 2020 at 16:15
  • What people believe doesn't matter as much as what the procedure finds, does it? Everyone could be sure that the defendant is guilty, but if no sufficient evidence gets delivered on the stand, the jury/judge will acquit them.
    – Greendrake
    Commented Dec 7, 2020 at 22:26
  • 3
    @Greendrake I am saying that the out of court state is not made under oath but that person recounting the out of court statement in the courtroom is under oath. Such a statement is frequently admissible as evidence. The fact that someone says something to a cop outside the courtroom without being under oath doesn't make the out of court statement not admissible as evidence. It might be hearsay but there are many exceptions to the hearsay rule, some of which would probably apply in this example.
    – ohwilleke
    Commented Dec 8, 2020 at 0:34
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    If you've got evidence for witness tampering, you might not need the mistrial. The normal process of impeach the witness should be capable of bringing that evidence to light, and it won't look good for the defendant.
    – Joshua
    Commented Mar 14, 2023 at 15:13

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