§ 22.01 Introduction

• Jurisdiction: United States

§ 22.01 Introduction

Credibility refers to a witness's worthiness of belief. Assessing the credibility of a witness is a classic jury function. As one court remarked, "Sorting truth from fiction, of course, is for the jury."¹ In assessing credibility, the jury may consider a multitude of factors.²

[A] Stages of Credibility

Credibility may be viewed in three stages: (1) bolstering, (2) impeachment, and (3) rehabilitation. Impeachment involves attempts to diminish or attack a witness's credibility. There are also rules regulating attempts to support credibility. For example, as a general matter, a witness's credibility may not be bolstered (supported) prior to impeachment. Moreover, under certain circumstances, a witness's credibility may be rehabilitated (supported) after impeachment. Thus, bolstering and rehabilitation both involve efforts to support credibility; the difference is one of timing.

[B] Types of Impeachment

Numerous factors may be considered in evaluating credibility, including a witness's demeanor while testifying.³ There are, however, five principal methods of impeachment: (1) bias or interest, (2) sensory or mental defect, (3) character for untruthfulness (which includes impeachment by reputation, opinion, prior convictions, and prior untruthful acts), (4) specific contradiction, and (5) prior inconsistent statements (self-contradiction). There are specific Federal Rules on only some these methods.⁴

Moreover, Rule 610 prohibits using a witness's religious beliefs to impeach, and a special impeachment rule on learned treatises applies to experts.⁵ In addition, hearsay declarants may be impeached.⁶

[C] Extrinsic Evidence ("Collateral Matters")

Depending on the method, impeaching evidence may be elicited on cross-examination⁷or through other witnesses, which is known as extrinsic evidence.⁸ The admissibility of extrinsic evidence depends on the type of impeachment—whether the method is considered "collateral." The word collateral is confusing; in this context, it is a conclusory label.⁹ If impeachment is collateral, extrinsic evidence is prohibited. If not, extrinsic evidence is admissible. The best approach would be to avoid the word collateral and simply ask if extrinsic evidence is allowed.

There are some blanket rules in this context. Some types of impeachment, such as bias, were never considered collateral at common law, and therefore extrinsic evidence was always admissible.¹⁰ In contrast, other types of impeachment are always considered...