Let's say I've been accused of a murder. Throughout the investigation I've plead the Fifth as to where I was when the crime happened. Eventually I'm put on trial, still pleading the fifth as to my whereabouts during the crime.

Then, when put on the stand during the trial, I finally tell the court, and jurors, that I had an airtight alibi the entire time and have just refused to share it until now. Let's say the alibi could result in some trivial criminal charges being filed, like loitering, so I do have the right to claim I had reason to fear bearing witness to myself.

I'm wondering what would happen at this point. The prosecution wouldn't have had a chance to prepare for this revelation, but they can't say that I or my lawyer acted wrongly if I only now decided to testify. Would this be cause for a mistrial?

Would it matter if this was a legal strategy? For instance what if I tell my lawyer "I don't want to reveal my alibi unless you think there is a greater then 50% chance the jury will find me guilty." Can my lawyer continue as normal, knowing I may surprise the defense if I deem the odds of going to jail too high, or is he in a position where he has to say something once he knows I'm intentionally withholding information to surprise the prosecution?

As to why anyone would do this, I can think of two reasons. 1) I know who did it and was willing to take the chances at court to protect the real person until it became clear I'll likely lose, 2) I did the crime, but the prosecution has the theory of the crime all wrong, and so I'm intentionally looking to undermine the prosecution by surprising them with an alibi in hopes of convincing the jury that the prosecution didn't do their 'homework' and thus I'm innocent.

  • 5
    "when put on the stand during the trial": it's usually not a good idea to testify at your own trial (especially if you committed the crime, as the last paragraph suggests might be the case). If you can introduce evidence establishing your "airtight alibi" without your own testimony, that would be preferable (and more credible).
    – phoog
    Nov 30 '20 at 23:07
  • @phoog I agree it's unlikely to be a good idea. Still it could happen, after all someone may get cold feet and decide to reveal an alibi that's likely to get them into some (lesser) trouble to get out of the current trial or something. I'm more curious how the court would handle it if it happened.
    – dsollen
    Dec 1 '20 at 0:39
  • Sounds like you were pleading the fifth to delay things while you came up with this "alibi".
    – Unfair-Ban
    Dec 1 '20 at 12:22
  • Not to mention it is never a good idea to not tell the absolute truth to your own attorney. Attorney client priviledge is designed specifically so your lawyer can know exactly what you were doing. Reason 1 is also faulty because you open yourself up to Accesory to the crime or Obstruction of Justice.
    – hszmv
    Dec 3 '20 at 12:28
  • UK law: "You do not have to say anything. But it may harm your defence if you do not mention when questioned something which you later rely on in court. Anything you do say may be given in evidence." So not telling about your alibi might hurt you in court.
    – gnasher729
    Dec 3 '20 at 17:13


Federal law and most states have an notice of alibi rule that requires a defendant to identify witnesses who will testify as to their alibi and where the defendant claims to have been.

The validity of these rules was upheld by the Supreme Court in Williams v Florida:

The Fifth Amendment would not be violated if, after the alibi witness had given evidence, the court granted a continuance to allow the prosecution to seek rebuttal evidence (this point was conceded by Williams's lawyers). Consequently, all the notice-of-alibi law did was allow the prosecution to do so before the trial, instead of having to interrupt the trial. It did not provide the prosecution with more information to use against a defendant than they would eventually get in any event.

  • 2
    I think the answer is more complicated than just “No.” It’s unlikely that a court would exclude evidence which actually shows the defendant to be innocent as a result of failure to comply with an alibi notice rule. As per the syllabus in Williams v Florida: “failure to comply can [not must] result in exclusion of alibi evidence at trial (except for the defendant's own testimony).”
    – sjy
    Dec 5 '20 at 3:23

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