When is extrinsic impeachment considered non-collateral?

Extrinsic impeachment is considered non-collateral when it pertains to bias. In the context of witness impeachment, bias refers to a motivation that a witness may have to favor one party over another in their testimony. This type of impeachment is non-collateral because it is directly relevant to the credibility of the witness and can potentially impact the outcome of the case.

In contrast to collateral matters, which do not affect the substance of the case and thus cannot be proved by extrinsic evidence, bias can influence a jury's perception of the witness's reliability. Therefore, extrinsic evidence can be introduced to establish a witness's bias, making the impeachment a crucial part of the case that can lead to a reassessment of the witness's testimony.

While other factors such as hearsay, party status, or character evidence can play roles in witness credibility, they do not serve the same foundational purpose in determining non-collateral impeachment as bias does.