Is it acceptable for a witness to give an answer to a question posed to him/her in court as I dont know or I'm uncertain?

This is not a refusal to testify it is just a lack of knowledge. Does the justice system allow for the option that a witness simply does not know the answer to a question?

Maybe it served no real purpose for parties to inquire about a topic that a witness is uncertain about.

What could happen if a witness is asked about the shoes a robber was wearing? The witness says I looked the robber in the eyes I did notice his shoes and his credibility as witness being questioned because how could you not look at the shoes?

  • 4
    Should it say "I did not notice his shoes"?
    – user35069
    Feb 21, 2022 at 11:20
  • 29
    How could it not "allow" for something like this? If the witness truly doesn't know, what could they do about it?
    – Barmar
    Feb 21, 2022 at 14:24
  • 17
    I could not tell you what kind of shoes anyone is wearing, including my wife, right now, whom I just saw 5 minutes ago. Lots of people don't notice other people's shoes. Feb 21, 2022 at 14:54
  • 8
    Lying in court is bad, mmkay? If you don't know the answer but you still gave an arbitrary answer that's lying, mmkay? Feb 21, 2022 at 20:16
  • 8
    Having been robbed at gunpoint with a sales counter between me and the robber, I can very definitively state that not only did I not observe the robber's shoes, it would have implausible for me to see the shoes at all.
    – Randall
    Feb 21, 2022 at 22:15

5 Answers 5



"I don't know" answers are quite common in trials, and are perfectly acceptable. Indeed in some cases the aim of a question, particularly on cross examination, may be to get a witness to admit that s/he does not know something that it was earlier implied that the witness did know.

An ideal witness will not claim to know something that s/he does not in fact know, although many witnesses feel that they must give a definite answer, even when they lack definite knowledge. A judge may instruct the witness to make a definite answer only if the witness is certain.


In addition to David's answer - it's more than acceptable for a witness to say that they don't know the answer; it's a requirement of their oath / affirmation to say "I don't know" if they are telling:

...the truth, the whole truth, and nothingbut the truth..

  • 2
    @NeilMeyer Possibly, but looking at eyes and not shoes could be a result of something akin to the weapon focus effect.
    – user35069
    Feb 21, 2022 at 11:19
  • 11
    @NeilMeyer if the answer is inconsistent with other evidence then it calls the witness credibility into question irrespective of what kind of answer it is. A witness introducing themselves as an ordinary observer might be called into question for failing to notice something they should be expected to noticed, for noticing something in more detail than could be reasonably expected, or for claiming to notice a detail that is contradicted by other evidence. Whether the answer is a statement of knowledge or lack of knowledge doesn't change whether it can or should be questioned.
    – Will
    Feb 21, 2022 at 16:18
  • 1
    @NeilMeyer Call the credibility into question because they don't know something?
    – Joe W
    Feb 21, 2022 at 18:49
  • 1
    Often, a bad "I don't know" can be fixed by a competent attorney, asking for the reason something is unknown or where the focus lay: "Why do you not know the color of their shoes?" "They stood in front of the counter and I could not see them"/"I was looking at their face."
    – Trish
    Feb 21, 2022 at 20:20
  • 2
    It might call the credibility of the lawyer into account. Generally, in law as in journalism, it's always risky asking a question that you yourself don't know the answer to. A good lawyer will ask questions with an expectation for a response that helps their case. So getting an "I don't know" response from a witness is useful to the lawyer only if it hurts the credibility of the witness, e.g. if it's a hostile witness. Getting "I don't know" from a friendly witness is bad for the lawyer - they should've known that was coming and not wasted time asking that question. Feb 22, 2022 at 16:02

Banning 'I don't know' would be contrary to witnesses needing to be truthful

Let's propose the following question asked by an attorney (and it would have a good reason to be asked, with the answer being material to the case):

"Witness, what is in this box?"

The witness could know it and then would need to answer with that information. But the witness could also not know it, and then would be required to tell so — because they are not allowed to guess. So, our witnesses might answer truthfully with any sentence that transfers that information that they don't know. Be it "I don't know", or a more elaborate way like "Whatever you have put into the box, Mr. Attorney. I can't know what you have put into the box there" would also be allowable.

However, if witnesses would be banned from saying that they didn't know something, it would force them to invent stuff that is not truthful — and thus directly contradictory to the duties of a witness! This is especially true in that a witness may only not answer a question if they would make themselves (or in some jurisdictions also close relatives) the suspect of a crime.

  • (I suppose an alternative to lying — and hence committing perjury — would be for a witness to keep silent. But I guess that could ultimately be taken as contempt of court…?)
    – gidds
    Feb 21, 2022 at 21:10
  • 1
    @gidds The witness may not stay silent usually: the court will order to answer the question.
    – Trish
    Feb 21, 2022 at 21:30
  • 3
    If the witness knows and doesn't know what's in the box at the same time, would it be a case of Schrödinger's court?
    – user35069
    Feb 21, 2022 at 21:58
  • 1
    @Rick of course we can't open the witness, that'd be battery. But we can ask the question and observe how the court-wave collapses.
    – Trish
    Feb 23, 2022 at 10:33

Part 1 Title 7 Chapter 5 Section 125 of the California Penal Code states:

An unqualified statement of that which one does not know to be true is equivalent to a statement of that which one knows to be false.

When one makes an unqualified statement of X, one is implicitly stating that one knows that X is true. Thus, if you don't know that X is true, such a statement is perjury. Ultimately, a witness' testimony is not of what is true, but what they have personal knowledge of (or, in the case of an expert witness, what opinion they have, informed by their personal knowledge of the events of the case and their professional expertise). If you don't have personal knowledge of a fact, then it is inappropriate to give unqualified testimony to that fact. If not misleading the trier of fact as to one's level of knowledge causes the trier of fact to give less credence to one's testimony, so be it. Intentionally giving misleading testimony to make oneself seems more credible is perjury.

If a party doesn't have a reasonable expectation that the witness would have personal knowledge of the matter, then it's inappropriate for them to ask the question in the first place, and the other party can object to the question (e.g. "Objection: calls for speculation"). For instance, if a cop comes in after the robber was subdued by a security guard, and after the security guard has taken the robber's gun away, and a lawyer asks the cop "What hand was the robber using to hold the gun?", that would be improper, as there would be no way for them to answer that without engaging in speculation or hearsay.

  • 'An unqualified statement of that which one does not know to be true is equivalent to a statement of that which one knows to be false.' That's beautiful. Can we adopt that principle outside the courtroom, too, please? Feb 22, 2022 at 11:21

There would be many situations where it is impossible for the witness to know the answer, such as conversations in a foreign language, or over the phone, or details not visible to the witness.

You can also have situations where the witness cannot understand the question, such as when jargon is being used. Alternatively, the question might involve a matter of judgement or opinion, though that is usually objected to.

Even Expert witnesses will say they don’t know, though they’re more likely to express it as not being qualified to answer.

So yes, of course it’s OK to plead ignorance.

Of course, if the answer is “I don’t know” too often, you might question why the witness was called at all. That’s often the intention in cross examination, of course.

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