What does it mean when a witness is impeached?

When a witness is impeached, it refers to the process of challenging or discrediting their credibility and reliability in the eyes of the court or jury. This can occur when the testimony they have provided is contradicted by additional evidence or prior statements, raising doubts about the truthfulness or accuracy of what they have said. Impeachment serves to highlight inconsistencies or dishonesty, which can undermine the overall impact of the witness's testimony on the case being presented.

In this context, the emphasis is on the presence of sufficient proof that contradicts the witness’s testimony, making option B the most accurate description of what it means to impeach a witness. Other choices do not reflect the essence of impeachment; for instance, supporting a witness's credibility or having an unblemished record does not correlate with the act of impeachment itself. Moreover, refusal to provide testimony indicates a different scenario altogether, unrelated to the concept of impeachment.