Which of the following is a valid basis for impeaching a witness's credibility?

• A. Interest and bias
• B. Hearsay
• C. Opinion
• D. Evidence of chain of custody

Answer: (A)

Impeaching credibility centers on showing factors that could color a witness’s memory or truthfulness. A valid basis is bias or interest—when a witness has a personal stake in the outcome, their testimony may be influenced by that stake, making it less reliable. For instance, a witness who stands to gain financially or who has a close relationship with one party may not be objective, so their statements warrant careful scrutiny in cross-examination.

Hearsay isn’t a standalone basis to attack credibility; it concerns whether out-of-court statements are admissible for truth and doesn’t by itself prove the witness is untruthful. An “opinion” about someone’s truthfulness isn’t itself a recognized impeaching ground in the same direct way as bias. Chain of custody speaks to the authenticity and handling of physical evidence, not to the witness’s reliability or honesty.

So the reason bias or interest is the best choice is that it directly targets the reliability of the witness by exposing a motive that could distort testimony.