State v. Victor K. Johnson, 2004 WI 94, affirming unpublished decision of court of appeals
Issue: Whether the State impermissibly cross-examined the defendant about the truthfulness of another witness.
¶2. We conclude that the purpose and effect of the prosecutor’s cross-examination of Johnson was to impeach Johnson’s credibility, not to bolster the credibility of another witness, because both Johnson and the other witness were testifying to their personal observations about the same events. Therefore, the cross-examination of Johnson was permissible. …
There are, the court says, two lines of cases addressing whether one witness may comment on another witness’s testimony: an expert commenting on direct, State v. Haseltine, 120 Wis. 2d 92, 352 N.W.2d 673 (Ct. App. 1984); and eye-witness testimony on cross, State v. Jackson, 187 Wis. 2d 431, 523 N.W.2d 126 (Ct. App. 1994). ¶13. The court preserves the Haseltine rule (an expert can’t comment on the credibility of another witness), but draws the line there:
¶19. We perceive no conflict between the Haseltine and Romero line of cases and those headed by Jackson and Bolden. In the Haseltine line, the objected to testimony is simply bolstering another witness’s testimony of an event about which the expert witness has no personal knowledge. It is generally done on direct examination and usurps the jury’s role as the “lie detector in the courtroom.” See Haseltine, 120 Wis. 2d at 96. The jury can independently determine the credibility of each witness, see Romero, 147 Wis. 2d at 278, and does not require an expert witness to assist it with that determination.¶20. By contrast, in the Jackson line of cases, two witnesses are testifying about an event that both claim to have seen, and their testimony conflicts. The purpose5 and effect of the cross-examination of the second witness is to test that witness’s credibility through his or her demeanor and answers to questions. It aids the jury in its truth-finding function. See Wis. Stat. § 906.07 (2001-02) (stating the credibility of any witness may be attacked by any party). The testimony elicited by the prosecutor in Bolden and Jackson was not placed before the jury to bolster the credibility of the other witnesses. Instead, cross-examination was used to highlight the inconsistencies in the testimony, and give the witness an opportunity to explain those inconsistencies. Bolden, 265 Wis. 2d 853, ¶8; Jackson, 187 Wis. 2d at 437-38. As the court of appeals concluded, the questions posed “were solely to impeach [the defendant’s] credibility.” Jackson, 187 Wis. 2d at 437. Such questions may help the jury assess the credibility of witnesses. Bolden, 265 Wis. 2d 853, ¶8. Such a technique is permissible cross-examination.6
Not clear just why it mattes whether the witness was an eyewitness or an expert; why, that is, the one usurps the jury function but the other doesn’t; after all, each is called upon to assert whether or not another witness is telling the truth. But there you have it nonetheless. Apparently, for whatever reason, it does matter whether the witness called upon to comment was an eyewitness – thus, the court stresses that both the defendant and the witness he was required to comment upon were eyewitnesses to the crime. ¶23. (What if the defense were alibi? Presumably, this inquiry would be impermissible.) The court also stresses that the sole purpose of this sort of inquiry is impeachment. This limitation seems to rest on a fairly arcane and for that matter unexplained distinction (“So, you’re saying that Witness X was lying when she said that you …” has just what limited meaning? that the defendant’s answer is only relevant to whether X was truthful when she said he had committed the crime?). But for whatever good it might do, presumably you’d be entitled to a limiting instruction of some sort under § 901.06. If you manage to craft one, by all means share it. (“The testimony of the defendant that X lied when testifying that defendant had committed the crime is limited to assessing defendant’s credibility in denying that he had committed the crime, and may not be used for any other purpose.”)
One other point. The court of appeals has held that the State can’t simply interject in closing argument, for the first time, a claim that the defense is asserting that the witnesses against him are lying. State v. Steven T. Smith, 2003 WI App 234 (in that instance, that the police must have been lying). That result probably survives this one, because it was based on different considerations, namely lack of any evidentiary support or of invited response.)