Impeachment of a witness refers to the process of discrediting or undermining the credibility of a witness during a trial, by presenting evidence or asking questions that contradict their testimony or reveal a bias, inconsistency, or falsehood in their statements. It is a common strategy used by attorneys to challenge the veracity of a witness and to cast doubt on the reliability of their testimony. In federal court, Federal Rules of Evidence 607 provides that any party may attack the credibility of a witness by introducing evidence that reflects on the witness's character for truthfulness, prior inconsistent statements, bias, interest, or other reasons.
The Supreme Court has also held that a party can impeach a witness by cross-examining them about specific instances of conduct that show their lack of credibility, as long as the questions are related to the witness's character for truthfulness. This rule was established in the case of Davis v. Alaska, 415 U.S. 308 (1974), where the Court held that a defendant's right to confrontation and cross-examination includes the right to ask a witness about their juvenile criminal record to show their bias and motivation to testify.
[Last updated in February of 2023 by the Wex Definitions Team]