Does a witness admit perjury by testifying a different story on retrial?

Question

Bob was a witness in a trial. That trial was later declared a mistrial and a new one was ordered.

When taking the witness stand again, Bob tells a whole different story, inconsistent or directly opposite to what he testified in the original trial.

• Can his original testimony be even referred to in the new cross-examination? Or is that rendered inadmissible due to the whole original trial being a nullity?
• Does he effectively admit committing perjury by claiming he is saying the truth now, inference being that he was lying under oath previously?

(Any common law jurisdiction)

Answer 1

Bob should certainly expect to be impeached by whichever side his testimony injures. Their attorney will confront him with the transcript of his previous testimony, and likely read it out loud for the jury to hear, and force him to acknowledge that he said something different before. This is pretty standard trial tactics.

Bob would not be treated as formally admitting that he committed perjury, though I think it's fair to say that he has effectively made that admission. One side will treat him as having lied the first time; the other will treat him as lying now. It's possible that he will have some explanation for the discrepancy -- he was high, he has memory problems, he misunderstood the question -- but in your hypothetical, the explanation would have to be pretty amazing to justify such a complete reversal.

Answer 2

Can his original testimony be even referred to in the new cross-examination?

No.

Or is that rendered inadmissible due to the whole original trial being a nullity?

No. It’s rendered inadmissible because it is hearsay - a statement made by the witness outside this trial. Unless there is some exemption to the hearsay rule (e.g. because it contained admissions or a confession) it’s inadmissible.

Does he effectively admit committing perjury by claiming he is saying the truth now, inference being that he was lying under oath previously?

No.

Perjury is not just swearing a falsehood. To be perjury, the falsehood must be material and must be a deliberate lie (an untruth spoken knowing that it is untrue).

Like most other crimes in the common law system, to be convicted of perjury one must have had the intention (mens rea) to commit the act and to have actually committed the act (actus reus). Further, statements that are facts cannot be considered perjury, even if they might arguably constitute an omission, and it is not perjury to lie about matters that are immaterial to the legal proceeding. Statements that entail an interpretation of fact are not perjury because people often draw inaccurate conclusions unwittingly or make honest mistakes without the intent to deceive. Individuals may have honest but mistaken beliefs about certain facts or their recollection may be inaccurate, or may have a different perception of what is the accurate way to state the truth. In some jurisdictions, no crime has occurred when a false statement is (intentionally or unintentionally) made while under oath or subject to penalty. Instead, criminal culpability attaches only at the instant the declarant falsely asserts the truth of statements (made or to be made) that are material to the outcome of the proceeding.

To prove perjury, it is not enough to show that the statements are inconsistent. The prosecution must show they were material to the trial (i.e. they must be about guilt or innocence) and the defendant knew they were lying at the time they were spoken. A defendant who has “changed their mind” over the passage of time cannot be said to be lying in either trial. They believed X then, now they believe Y - that’s not perjury even if X or Y or both are untrue. One of them being false is a necessary but not sufficient condition for perjury.