Witness impeachment

Witness impeachment, in the law of evidence of the United States, is the process of calling into question the credibility of an individual testifying in a trial. The Federal Rules of Evidence contain the rules governing impeachment in US federal courts.

Under the common law of England, a party could not impeach its own witness unless one of four special circumstances was met. The Voucher Rule required the proponent of the witness to "vouch" for the truthfulness of the witness. Here are the special circumstances:

The rule has been eliminated in many jurisdictions. Under the US Federal Rules of Evidence, Rule 607 permits any party to attack the credibility of any witness.

In the US, a party has the option of discrediting a witness through impeachment by cross-examining the witness about facts that reflect poorly on the witness's credibility or, in some cases, by introducing extrinsic evidence that reflects negatively on the witness's truthfulness or knowledge.

A party may impeach a witness in the US by introducing evidence of any of the following (remembered via the mnemonic BICCC)

Courts permit parties to cross-examine a witness in order to impeach that witness based on demonstration of bias. Witness bias may be catalyzed by any number of circumstances, ranging from the witness's blood relationship to a party to his financial stake in the outcome of the litigation. Most US jurisdictions require a cross-examiner to lay a foundation before extrinsic evidence can be used to demonstrate bias for impeachment purposes. Although Rule 610 provides that evidence of a witness's "religious beliefs or opinions is not admissible to attack or support the witness's credibility," an inquiry into the witness's religious beliefs or opinions for the purpose of showing interest or bias because of them is not within the rule's prohibition.

If a witness is accused of bias, and there is an opportunity to cross-examine during the current trial, any statements made at a previous trial/hearing and which are consistent with the testimony at the present trial are admissible, not hearsay.

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