How can bias be invoked to impeach a witness, and why is bias material to credibility?

• A. By showing relationships, financial or personal interests or motives that could affect credibility; bias affects reliability of testimony.
• B. By showing the witness's favorite color.
• C. By presenting the witness as an expert on an unrelated topic.
• D. By using only hearsay evidence.

Answer: (A)

Bias is invoked to impeach a witness by showing relationships, financial interests, or personal motives that could influence their testimony. When a witness stands to gain or lose something depending on the case outcome, that incentive can cause them to distort or select the truth, which undermines the reliability of what they say. Because credibility measures how trustworthy or objective a witness is, revealing bias explains why their testimony should be weighed with caution and often given less weight.

The other options miss the point. A favorite color has no bearing on credibility. Presenting someone as an expert on an unrelated topic doesn’t demonstrate bias against or for a party. And relying on only hearsay doesn’t address the witness’s bias or reliability.