Suppose you firmly believe something to be true but you know that it can be proven false beyond a reasonable doubt. This can happen if, for example, you witnessed something that is incredibly unusual. It might also happen if enough other people conspire to lie about something that you know the truth about.

The fifth amendment to the constitution should prohibit you from being forced to testify in a situation where you have a reasonable belief that truthful testimony could subject you to prosecution for a crime. But it seems like that can't help you in this case. Immunity from prosecution for truthful testimony won't help you if a prosecutor can prove beyond a reasonable doubt that your testimony is false. And I can't imagine a prosecutor allowing someone to testify with immunity from prosecution for making false statements in that very testimony.

This can't be so rare it has never happened. If it has happened, what happens when someone tells a judge that he pleads the fifth because he believes that if he gives the testimony he believes is truthful it will subject him to perjury charges because it can be proven false beyond a reasonable doubt (despite his belief that it is true)? If it has never happened, what should happen in this case?

To be precise, the assumption behind this question is that you have an objectively-reasonable belief that an answer that you believe is true would subject you to criminal liability for perjury.

To be clear:

  1. The person has not yet testified.
  2. They are being asked to testify.
  3. They have an objectively-reasonable fear that the testimony they would give will subject them to criminal liability for perjury.
  4. They therefore invoke their fifth amendment right.

Assume none of these points are controversial. Obviously, others may not agree that the testimony they say they will give is truthful. But there is no reason to doubt their claim that the testimony they would give would subject them to criminal liability for perjury.

The question is whether this has ever occurred and, if so, what happened. Or, if it has not occurred, what would happen next? Can the person be granted immunity from prosecution for perjury in the very testimony they are given? Or can they be compelled to testify even though they have an objectively-reasonable belief that the testimony they would give will subject them to criminal liability? Or is there some third alternative?

Lastly, if this has never happened, why not? It seems like this wouldn't be a terribly uncommon situation. I don't think it would happen every day or even every year -- but never in the history of jurisprudence?!

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    It's not perjury if you believe it to be true, even if you are wrong. So to convict you, the prosecution not only has to prove beyond a reasonable doubt that your testimony was false, but that moreover you didn't believe it yourself. Feb 28, 2019 at 22:13
  • Anyway, I think the theoretical answer to this question is going to be simple: the law requires you to testify what you believe to be true, and to trust the legal system not to wrongfully convict you of perjury. Of course, as you've set up the situation, you could also lie and get away with it. Feb 28, 2019 at 22:32
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    @NateEldredge You are correct that you cannot be convicted of perjury unless it can be proven beyond a reasonable doubt that you knew that what you were saying was false. However, one cannot know what future evidence might be uncovered and so a fear of criminal liability for saying something you know can be proven false could easily be objectively reasonable even if you aren't currently aware of any way it could be proven that you knew it was false. There's no way you can know what other evidence prosecutors might have or get and enough of the elements of the offense are known provable. Mar 1, 2019 at 6:41
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    @DavidSchwartz That fails the "reasonable person" test and falls straight into the "where's my tinfoil hat ohgodherecomesthelizardpeople!" territory. Mar 1, 2019 at 7:09
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    @zibadawatimmy These are utter fictions that the law has to insist is true -- that reasonable people don't fear being prosecuted for crimes they didn't commit and that reasonable people always know when they commit a crime. Otherwise, no testimony could ever be compelled. I think I'm a pretty reasonable person and I've testified a few times. Every time I worried that some mis-statement or erroneous recollection might subject me to criminal liability and even was specifically warned about this by my own attorneys every time. I guess nobody's reasonable. Mar 1, 2019 at 15:15

3 Answers 3


The California jury instructions for the crime of perjury give more detail on what it means to commit perjury: it's not just that you make a statement that is false, you have to willfully state that the information is true even though you know it is false. If you have a belief that you will be convicted for perjury (or any crime) by testifying, you may invoke your 5th Amendment right (I assume you are not testifying as the defendant in a criminal matter). You might (theoretically: see below on immunity and perjury) be granted immunity from prosecution, in which case there is no 5th Amendment right to refuse to testify (you are not putting yourself in criminal jeopardy), and the court can order you to testify. Or, you might not be granted immunity and still be ordered to testify.

The federal immunity statute, 18 USC 6002, also needs to be scrutinized. When ordered to testify, "the witness may not refuse to comply with the order on the basis of his privilege against self-incrimination", but it generally cannot be used against him:

no testimony or other information compelled under the order (or any information directly or indirectly derived from such testimony or other information) may be used against the witness in any criminal case

However, there is an exception:

except a prosecution for perjury, giving a false statement, or otherwise failing to comply with the order.

In other words, you cannot be immunized against a perjury charge.

In Kastigar v. United States, 406 U.S. 441 defendant refused an order to testify, on the grounds that they (allegedly) believed that the government's grant of immunity was not broad enough, i.e. that there were areas where they might be questions and forced to criminally implicate themselves. They refused, and were held in contempt.

The opinion recognized that the 5th Amendment "protects against any disclosures that the witness reasonably believes could be used in a criminal prosecution or could lead to other evidence that might be so used" (emphasis added).

In Mason v. United States, 244 U.S. 362, the court held that

The Fifth Amendment does not relieve a witness from answering merely on his own declaration or judgment that an answer might incriminate him; whether he must answer is determinable by the trial court in the exercise of its sound discretion, and unless there is reasonable ground, as distinct from a remote or speculative possibility, to apprehend that a direct answer may prove dangerous to the witness, his answer should be compelled.

Heike v. United States, 227 U.S. 131 asserts that "the constitutional protection is confined to real danger, and does not extend to remote possibilities out of the ordinary course of law, citing Brown v. Walker, 161 U.S. 591 (itself quoting Lord Chief Justice Cockburn):

"the danger to be apprehended must be real and appreciable, with reference to the ordinary operation of law in the ordinary course of things; not a danger of an imaginary and unsubstantial character, having reference to some extraordinary and barely possible contingency, so improbable that no reasonable man would suffer it to influence his conduct"

Although the wording of the immunity statute does not allow immunity from prosecution for perjury, the 5th Amendment right can only be invoked against a real legal jeopardy. They can be compelled to testify, they probably cannot be immunized against a perjury conviction (certainly not at the federal level). We would need to know the entire circumstances of the case to be able to assess whether the "knowing to be false" part could be proven beyond a reasonable doubt.

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    Not sure if the CA stuff is relevant, but in other comments the OP has stated the question as: can they be compelled even if they have an objectively reasonable fear they may be prosecuted for it? And the last part of your answer seems to address this, with those precedents indicating that an objectively reasonable fear is covered by the 5th. So +1. Mar 1, 2019 at 2:23
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    "you have to willfully state that the information is true even though you know it is false." Actually, it's enough to not have a reasonable basis for thinking that it is true; knowing that it is false is not necessary for a conviction of perjury."The federal immunity statute, 18 USC 6002, also needs to be scrutinized." There is not just statutory protection, but constitutional. Miranda rights would apply to any compelled statement (if you are specifically told that you do NOT have the right to remain silent, then that's the opposite of being Mirandized). Mar 1, 2019 at 18:17

So the other answers are very good, but I'd like to put it to a practical scenario. Suppose you are testifying against Bob (you are a witness for the prosecution) who is being tried for the murder of Alice. You testify you saw Bob kill Alice and run away. You could identify it was Bob because you and Bob are coworks. You see him every day, and you don't talk to him often, but you recognize him anywhere.

Then the defense comes from Cross-Examination and asks "Are you aware that Bob has an Identical Twin Brother, Charlie?" So here is a situation you discussed: You testified to something that many not be factually true. You identified Bob as the murder, but the possibility exists that Charlie killed Alice. (At this point, we haven't proven Bob did not kill Alice, or the Charlie did. All we did was raise a doubt that Bob killed Alice showing that Charlie could have done it.).

If you were unaware, this is not perjury, the defense is just trying to impeach you as a witness (has nothing to do with your political office... Impeaching is basically showing the jury that there are reasonable doubts to your claim). To the best of your knowledge Bob was not an identical twin... thus, seeing Charlie would logically cause you to believe it was Bob.

If you were aware of this, this still doesn't mean you perjured yourself. After all, anyone who has ever met a set of twins can tell you that they aren't 100% identical. Bob could have a scar that Charlie does not, thus you could say you saw the scar. Charlie could live on the other side of the country and you weren't aware he was in town that night. Perhaps it was late night at the office and Bob has the key but Charlie, who doesn't work there, wouldn't have the key.

If you were aware that Bob had a twin, it could be when you called the police, you told them it was either Bob or Charlie and through detective work, the police arrested Bob, and not Charlie. Here, in your testimony, you probably should have said you told the cops that it was one of the twins, but the fact is they relied on your reporting to make a case against one twin, the one here. You would know that the case is against Bob by the name of the case (People vs. Bob) or reporting in the news. Here the prosecutor is more at fault than you because he should have coached you to say "one of the twins" and not Bob and avoid this, but as a lay person who wouldn't know that much, this is probably not intentionally lying. Likely the Prosecutor who gets into this situation during a Re-Direct by asking you if you knew at the time you talked to the police if Bob committed the crime and/or Are you only referring to Bob in testimony because he is on trial? (The first verifies that your testimony was identifying the pair and the reasonable explanation for referring to bob in testimony when you didn't know at the time.).

In order for this to be perjury, you would have A) know that Bob had an identical twin brother Charlie AND B) knew that Charlie killed Alice, but testified that it was Bob OR C) identified Bob and only Bob because you don't like Bob for some reason.

If we break this down, into a truth table of sorts, where 1 is true and 0 is false, then the following proposition for perjury is as follows:

A && (B || C) = 1

This means that A MUST ALWAYS BE 1. It's possible for A = 0, B = 0 and C = 1, but that means that 0 && (0 || 1) = 0 && 1 = 0. Since 0 is false, you didn't perjure yourself It's impossible for A = 0, B = 1 and C = 0 which becomes 0 && (1 || 0) = 0 && 1 = 0. This is logically false in proposition and down right impossible by the proportions. You cannot simultaneously not know Bob had a twin and know that it was Bob's twin brother who committed the crime.

If you knew Bob had a twin and identified both twins to the investigators but testified about Bob being the killer, then the question is A = 1, B = 0, and C = 0. Which will result in the final metric being 1 && 0 which will equal 0.

Only a situation where A = 1 and either B or C or both equal 1 in order for this to be perjury.


With respect to comments, of uncertainty of B or C testimony, this is why you will often here witnesses say something to the effect of "to the best of my recollection/knowledge" or "The event occurred on or around [a date]" these statements are used as basic excuses to say "I'm not fully sure about the answer, but I'm giving you the best one I have". For example, the answer to the question "When was the U.S. Declaration of Independence signed?" answering "July 5th, 1776" is wrong and perjury. However, if I didn't have the best knowledge of the subject and said "On or around July 5th, 1776", I haven't told the truth, but more importantly, I haven't lied. The document was really signed on July 4th, 1776, so it was in fact signed "On or around July 5th, 1776".

In order to be false you must prove that A) It was not signed on July 5th, 1776 OR B) it was signed on a date that is reasonably close to the date of July 5th, 1776.

So this means that A = 0 (it's false) and B = 1 (True). Our equation to prove this is false would be:

A || B = 0

Since this is an or Statement, only one statement needs to be true for the entire statement to be true. Since B is factually correct, it doesn't matter that A is false, the entirety of my statement is True.

Now, I haven't discussed another component of perjury, you also have to demonstrate that the false testimony is malicious in nature. In our original scenario, Bob's defense says Bob secretly recorded himself telling the witness about his twin brother prior to the crime occurring. When his lawyer asks if Bob ever told you he has a twin, and you answer No, then the Defense can present the evidence that you are wrong, opening yourself up to perjury. However, if the answer is "Not that I recall", the statment is not perjury.

Basically, here to prove perjury, you have to prove A) You had a conversation with Bob about his twin brother AND B) you did recall it.

Since we have hard evidence that A = 1, the question hinges on B. That's harder to proven because. You could have remembered it and lied (B = 1) or you could have not been paying attention and never really registered the conversation mentioned a twin brother (B = 0). Either way, the truthiness of B cannot be reliably discerned. No lawyer on planet earth can read minds (in so far as I am aware). And since perjury is a crime you are accused of, the lawyer needs to prove you knowlingly lied. In absence of proof that you do recall this specific conversation, you are assumed innocent and thus B = 0.

For this statement, guilty would be such that

A && B = 1

AND statements, in logic are different from OR statements. In order for the statment to be true, Both A and B must be 1. If either one is 0, then the statement on a whole is 0.

Thus A = 1 and B = 0, then 1 && 0 = 0.

  • Right, but if you know it can be proven beyond a reasonable doubt that A equals 1 and you don't know what can be proven about either B or C, then you would have a reasonable fear that testifying that A equals zero it subjects you to criminal liability. The test is not that your testimony will definitely lead to your conviction of a crime you know you committed, it's whether you have a reasonable fear that the testimony could subject you to criminal liability. (Which I would argue you actually always have, but that's neither here nor there.) Mar 1, 2019 at 18:28
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    Well, if the lawyer who is calling you as a witness hasn't coached you as to what to say, it's never good. This is why you hear so many people in legal cases say "In so far as I can recall" or "On or around (date)". It's accounting for the fact that they are not 100% sure of a fact, but they reasonably certain of it. A good lawyer should coach you on saying this when you're not 100% certain. I'll edit in an example.
    – hszmv
    Mar 1, 2019 at 18:59
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    Well that's more about being a good witness in the particular case so attorneys on the other side don't confront you with slight inconsistencies to make you seem like a worse witness. Someone's not going to be charged with, much less convicted of, perjury because they gave an answer that was slightly incorrect. It is already understood that all your testimony is limited to what you can recall. Were you correct that these weasel words had anything to do with the possibility of a perjury conviction, people would always have a reasonable fear of a perjury conviction for omitting weasel words. Mar 1, 2019 at 19:13
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    @DavidSchwartz: Perjury is knowingly lying about factual information while under oath. If you say something is 100% true and it isn't that meets the lying criteria, they have to prove only one thing. Making it fuzzy is admitting the fact might not be 100% but this is what I think I know about it. If the critical thing that needs to be said in testimony is X occurred a month before Y (which has a hard date attached to it), it's less important if it wasn't exactly a month (29 days in a non leap year) but MORE important that it was still occurring some time ahead of Y's hard date.
    – hszmv
    Mar 1, 2019 at 19:47
  • @raiph: Which is why if you use the "weasel words". If I say Independence Day is on or around July 5th, it is not a factual statement, but it is admitting to not recollection to make a specific statement, but recall the date sufficiently to be close in my statement.
    – hszmv
    Mar 20, 2019 at 14:50

Unfortunately it is sometimes the case that something can be proved "beyond a reasonable doubt" so that a court will accept it, even though it is untrue. In such cases miscarriages of justice tend to occur.

Fist of all, you cannot "plead the fifth" to avoid answering a question just because you think that the answer will not be believed. The answer must at least potentially incriminate you, that is be usable against you as evidence of a crime. I suppose that even if you are just a witness, if the truth is sufficiently unbelievable that you fear a perjury prosecution for truthful testimony, that would qualify. I don't know of any case law on this exact point. There is lots of case law on self-incrimination in general, however.

It is true that if a witness invokes the privilege against self incrimination ("pleads the fifth"), is granted immunity, and then lies under oath, a perjury prosecution can be brought. Perjury is a hard crime to prove, and prosecutors are usually not eager to pursue such cases except in very serious matters, but they can do so when they think fit.

To convict a person for perjury, it must be proved to the satisfaction of the trier of fact (jury, or judge if a jury has been waived) that the testimony was false, and that the person accused knew that it was false when it was given. The "knowing" part will usually rest on circumstantial evidence, unless the accused confessed or was caught admitting it, perhaps to an accomplice. But there must be significant evidence of some sort indicating that the accused knew that the testimony alleged to be perjury was false. It is not enough to show that a witness made contradictory statements under oath at different times. The prosecution must show which is true, and show knowing falsehood.

It is worth noting that a grant of immunity under the Fifth Amendment does not usually confer absolute immunity for what ever crime is involved. It prevents the government from using the testimony given under the grant of immunity, either directly or as a source of leads to an investigation. The government must be "no better off" than if the testimony had not been given, as far as convicting the immunized witness. But if there is independent evidence, not derived from the testimony given under the grant, then the government may prosecute and perhaps convict the person who "took the fifth".

  • This just seems to restate the question and agree with that it could occur. Yes, all that is true. So what happens? Has this ever happened? Feb 28, 2019 at 23:34
  • @David Schwartz I don't know of, nor could i find, a case where anything like this has happened. As for what would happen, it depends. Would the prosecutor think it serious enough to bring charges of perjury? Perhaps. Would the Jury (or Judge) convict? it depends on the whole of the evidence. They might. If there was such a conviction, that would be a miscarriage of justice. That happens, but i don't know of one much like that described in the question. Feb 28, 2019 at 23:56
  • I think you misunderstand my question. The person hasn't yet testified. They invoke their fifth amendment right against self-incrimination. Then what happens? Can they be compelled to testify even if they have an objectively-reasonable fear that their testimony may put them at risk of criminal prosecution that is not cured by the grant of immunity? Mar 1, 2019 at 0:21
  • @David Schwartz I'm not sure. i havn't been able to find a case in point. I know that if a person tries to use the fifth to avoid testimony that doesn't plausibly incriminate them, the judge will require them to testify under penalty of contempt of court. I suspect that would happen in such a case, but I can't find any examples. Mar 1, 2019 at 0:30
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    @DavidSchwartz Well if this were happening before a grand jury the prosecutor could send the 5th-pleading person before a judge (the prosecutor wouldn't be there), and the person would have to explain to the judge what the basis of their claim is and the judge would then rule on the validity and either sustain their invocation of the 5th or order them to answer the question(s). Whether or not the judge would have any particular case law to help him decide your exact particular, I don't know. Mar 1, 2019 at 0:36

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