13. This evidence should be

The use of character evidence to prove how a person probably acted raises the most difficult problems of relevance, especially in criminal cases. Regarding «prior bad acts,» the traditional majority view is that, subject to discretionary control of the trial judge, a witness may be interrogated upon cross-examination with respect to any immoral or criminal act of his life that may affect his character and show him to be unworthy of belief. Inquiry into «bad acts» is permitted even though the witness was never convicted. Federal Rule of Evidence (FRE) 608 permits such inquiry, at the discretion of the court, only if the act of misconduct is probative of truthfulness (i.e., an act of deceit or lying).

The FRE does not contain any explicit «collateral issue» rule. However, the trial judge has general discretion under FRE 403 to exclude evidence whose probative value is substantially outweighed by «a danger...of confusing the issues...undue delay [or] wasting time[.]» This discretion allows the judge to keep out evidence that would, under the common law approach, be banned as extrinsic evidence of a collateral issue.

Where a witness makes a statement not directly relevant to the issues in the case, the rule against impeachment (other than by cross-examination) on a collateral matter applies to bar the opponent from proving the statement untrue either by extrinsic contradictory facts or by a prior inconsistent statement. The collateral issue rule, however, only applies where a second witness (or newly-introduced physical evidence) is used to impeach the principal witness. The rule does not apply where the impeachment of the principal witness occurs during the cross-examination of that witness and is carried out solely by the questions and the witness's answers. In other words, the rule is not truly a ban on «impeachment on collateral issues,» it is only a ban on «using extrinsic evidence to impeach on collateral issues.»

A is correct. As explained above, the prior bad acts of a witness can be inquired into during cross-examination if certain criteria are met. The expert witness's false testimony in his divorce proceeding is probative of his character for truthfulness or untruthfulness, and therefore can be inquired into upon in cross-examination.

B is incorrect. This answer reaches the correct answer with the wrong reasoning. It is not true that extrinsic evidence of false testimony may be admitted if it satisfies the standard of clear and convincing evidence. Rather, extrinsic evidence of prior bad acts would be inadmissible regardless of the level of substantiation. Prior bad acts regarding truthfulness may only be raised on cross-examination of the principal witness.

C is incorrect. The expert witness's character for truthfulness or untruthfulness is not considered a collateral issue, nor does it need to be affirmatively raised by the witness to be considered relevant. However, the proper form of impeachment by prior bad acts demonstrating untruthfulness is only on cross-examination.

D is incorrect. Although character evidence of prior bad acts is typically inadmissible to show conformity therewith, as explained above, prior acts showing untruthfulness may be raised on cross-examination for purposes of impeachment.