If witness testimony is shown to be demonstrably unreliable, can it be stricken?

Question

If a witness makes answers that indicate the witnesses testimony is entirely unreliable, can previous assertions of fact by the witness be stricken, or is it completely up to the jury whether to believe the witness or not?

For example, suppose the prosecution calls a witness who testifies that he saw the defendant at a bar on a particular Wednesday night.

Later, the defense cross-examines the witness and asks factual questions about the bar in question and the witness makes repeated mistatements in his answers. For example, under cross examination the witness claims he "parked in the bar's parking lot" and it turns out the bar has no parking lot. And he says he ate dinner at the bar that night, but it turns out that the bar does not serve food during weekdays. And so on, and so forth.

So, in this situation, where a witness makes multiple statements that are blatantly untrue, is it grounds for the rest of their testimony be stricken as demonstrably unreliable?

Answer 1

Whether a witness is credible is a matter of fact, whether to strike testimony is a matter of law

So, in a jury trial, the decision isn’t even made by the same person: juries decide matters of fact judges decide matters of law.

Testimony can be stricken because it’s inadmissible under the law: it’s hearsay, or opinion (for a non-expert witness) etc. Not because the witness is obviously wrong. I won’t say lying because that’s perjury - a serious allegation that would require evidence of intent to deceive the court.

Answer 2

Why do you need to strike the testimony¹? in fact, why do you even want to do that? A good lawyer would want to keep that testimony, as an indicator how bad the testimony was. As an indicator that the prosecution did not beyond a reasonable doubt prove their case. Let's ask Devin how to deal with a witness that you demolish so utterly that all he can say that he saw something but it's utterly unreliable? No wait, let's watch a movie together, where we do that with three witnesses! Yes, let's lawyer My cousin Vinnie, because in that regard, the movie is accurate to some degree. Have the witness agree with statements that dismember his credibility. Remember, the standard in a criminal case is beyond a reasonable doubt, as in, that nobody could reasonably believe the allegation was wrong. It's not by the preponderance of the evidence, as in a civil case, which means "more likely than not."

L: You were just ready to eat, and you heard a gunshot. That's right, I'm sorry. So, obviously, it takes you five minutes to make breakfast.

W: That's right.

L: Right, so you knew that. Uh, do you remember what you had?

W: Eggs and grits. [...]

L: Instant grits?

W: No self-respectin' Southerner uses instant grits. I take pride in my grits.

L: So, Mr. Tipton, how could it take you five minutes to cook your grits, when it takes the entire grit-eating world twenty minutes?

Is this witness believable? Can you believe the witness that had to see through dirt, a screen, and 7 bushes?! Can you believe the prosecutor's expert if all he can tell it was the most popular tire on the most popular car?

No? So if you can't believe these witnesses at all, how can there not be reasonable doubt?!

---

Ok, seriously, there are reasons when you want testimony gone. But in those cases, the testimony shouldn't have been in in the first place, because it is not admissable as evidence:

it was improperly obtained, it is prejudicial (the prejudicial value outweighs the probative value), it is hearsay, it is not relevant to the case, etc.

Conflicting statements only could become inadmissible if they make the whole witness irrelevant (not relevant) or everything is hearsay, but the fact of exposing the hearsay also points out very nicely that the persecution has a very very weak case. Also, the hearsay and opinion ban has holes, especially for experts.