Is extrinsic evidence allowed to prove bias for impeachment?

• A. Yes, bias may be shown by extrinsic evidence.
• B. No, extrinsic evidence is never allowed for bias impeachment.
• C. Extrinsic evidence is allowed only for sensory defects.
• D. Extrinsic evidence is never used in impeachment for any reason.

Answer: (A)

Bias goes to credibility because a witness who has a stake or interest in the outcome may testify with a motive to sway the result. Because bias is about a witness’s motive rather than the truth of a specific fact, you’re allowed to bring in extrinsic evidence to prove it. This means you can introduce outside facts, relationships, or other information that reveals the witness’s leaning toward or against a party, even beyond what questions on cross-examination might uncover. The aim is to show the credibility of the testimony is compromised by bias, not to prove the underlying facts of the case.

Extrinsic evidence for bias is not limited to a narrow category like sensory perception, which concerns how well someone perceived something. Sensory defects are a separate impeachment angle focused on the witness’s ability to observe, not on motive or allegiance. And stating that extrinsic evidence is never allowed for impeachment overlooks the well-established practice of using outside evidence to demonstrate bias. Therefore, extrinsic evidence may be shown to prove bias, making the best choice the one that allows this approach.