¶ 1. Under Wisconsin law, a witness may not testify that another physically and mentally competent witness is telling the truth. 1 1n the present case, David C. Tutlewski contends that this rule was violated when a State's witness testified that the complaining witness and her husband were incapable of lying. We conclude that this testimony was *382 inadmissible because it invaded the province of the jury. We therefore reverse Tutlewski's judgments of conviction and the order denying postconviction relief and remand for a new trial.
Background
¶ 2. On January 28, 1997, at approximately 7:00 a.m., Tutlewski entered the apartment of Michelle and Jeremy O. while Jeremy was at work. Tutlewski knеw Michelle and Jeremy through a mutual friend and he had visited the apartment on previous occasions. Michelle asked him to leave but he refused. Tutlewski then asked her if she would make love to him. She said "no" and told him to leave. When he refused, she attempted to call the police. Tutlewski yankеd the telephone from her, slapped her, and then held her down and forcibly had sexual intercourse with her.,
¶ 3. Tutlewski was subsequently charged with second-degree sexual assault by use of force contrary to § 940.225(2)(a), STATS., intimidation of a victim contrary to § 940.45(3), Stats., false imprisonment in violation of § 940.30, Stats., and burglary in violation of § 943.10(l)(a) and (2)(d), STATS., each as a repeat offender under § 939.62, Stats.
¶ 4. At trial, Jeremy and Michelle, both of whom are cognitively disabled, testified to the events occurring on January 28, 1997. Following their testimony and over Tutlewski's objection, the State called Charlotte Carver, Michelle and Jeremy's former high school special education teacher. Carver testified that she had been a teacher of the cognitively disabled for twenty-seven years, that she had taught Michelle for two years until her graduation in 1994 and that she had also instructed Jeremy. Carver described the difficulties cognitively disabled persons tyрically have with lan *383 guage and complex ideas and concepts. She explained that Michelle speaks slowly because "she needs extra time to process the information" and that the slow processing time would account for the long pause between questions asked of her and her answers. Carver testified that she got to know Michelle very well because she spent a significant amount of time with her inside and outside the classroom. The State's examination then concluded as follows:
Q. You said that in your estimation they were good people. Can you tell me this? Do you hаve an opinion concerning their reputation for truthfulness and honesty?
A. I think both Jeremy and Michelle are very honest, truthful young people, who I think are very naive to the deceitfulness of other people; and I don't think it is within their capabilities to lie or be deceitful. [Emphasis added.]
Tutlewski made no objection fоllowing Carver's response and he did not cross-examine her.
¶ 5. Tutlewski was found guilty of the charged offenses, except the burglary count. He then sought postconviction relief, arguing that his trial counsel was ineffective for failing to object to Carver's testimony that Michelle and Jeremy were incapаble of lying. The trial court denied his motion. Tutlewski appeals.
Discussion
¶ 6. Tutlewski contends that Carver's testimony should not have been permitted for two reasons. First, Tutlewski argues that the supreme court's recent decision in
State v. Eugenio,
A. Waiver
¶ 7. The State initially claims that Tutlewski waived his objection to Carver's testimony because he did not specifically object to her testimony during trial. We disagree.
¶ 8. Whether a party has raised an objection tо the admissibility of evidence sufficient to preserve the issue for appeal is a question of law that we review de novo.
See State v. Peters,
¶ 9. We are convinced that Tutlewski adequately raised his objection to Carver's testimony. Tutlewski first opposed the State's calling of Carver the day before trial. Tutlewski generally contended that there was no relevancy or basis for Carver's testimony. While no particular grounds were provided, Tutlewski made it known that he would later object to her being called.
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¶ 10. At trial and before Carver was permitted to testify, Tutlewski renewed his objection to the State's calling of Carver. Tutlewski maintained that the only reason the State was calling Carver was to bolster Michelle's and Jeremy's credibility, that such testimony was inadmissible under § 906.08, STATS., аnd that under
State v.
Kuehl,
*386 B. Haseltine
¶ 11. The central issue we address is whether Carver improperly testified that Michelle and Jeremy were incapable of lying. "The question of whether a witness has improperly testified as to the credibility of another witness is a question of law which we review independently."
State v. Huntington,
¶ 12. We begin our analysis with § 906.08(1), Stats., which provides that "the credibility of a witness may be attacked or supported by evidence in the form of reputation or opinion," with the condition that (1) the evidence only refer to character for truthfulness or untruthfulness, and (2) "evidence of truthful character is admissible only after the character of the witness for truthfulness has been attacked by opinion or reputаtion evidence or otherwise."
¶ 13. In the present case, Tutlewski specifically asked Michelle whether she had lied to her attorney or to police detectives. Michelle replied that she had not. In addition, Tutlewski inquired why she had not told anyone right away that she had been raped and whether she had previously had a sexual relationship with him. Michelle replied that she had been afraid to discuss the sexual assault with anyone and she denied having had a previous romantic relationship with Tutlewski. It is clear that Michelle's character for truthfulness had been attacked and Tutlewski does not dispute this issue on appeal.
¶ 14. Next,
Haseltine
places limits on the type of evidence that may be used to support a witness's character for truthfulness. Most notably, a witness is not permitted to express an opinion as to whether another physically and mentally competent witness is telling
*387
the truth.
See Haseltine,
¶ 15. In addition to expert witnesses, the
Haseltine
rule has also been applied to lay witnesses. In
State v. Romero,
¶ 16. To determine whether expert testimony violates the
Haseltine
rule, we examine the testimony's purpose and effect.
See State v. Pittman,
¶ 17. ■ As to the effect of Carver's testimony,
Sturdevant v. State,
The mental capacity of a witness is proper to be cоnsidered as bearing on [a witness's] credibility. Thus the impaired condition of the mind either from a temporary cause, ... or other infirmities, is deemed a proper subject of inquiry for the consideration of the jury in determining the credibility of a witness. So it may be shown that the witness has a mind or memory impaired from diseasе or other cause; but mere mental impairment, without more, is not sufficient to affect credibility ....
Id.
at 148,
¶ 18. Here, unlike in Sturdevant, it was the State, not Tutlewski, that presented evidence to explain Michelle's and Jeremy's cognitive disability. Rather than serving to impeach Michelle's and Jeremy's credibility, Carver's testimony sought to bolster their character for truthfulness. While Sturdevant permits impeachment of an impaired witness whose ability to perceive events or to tell the truth might be affected, it does not provide a corresponding basis to bolster a witness's testimony if the witness has a mental impairment. Although we believe it was appropriate for Carver to discuss the nature of cognitive disabilities and how such mental impairments аffected Michelle's and Jeremy's ability to testify or to recall particular facts, Carver's testimony that Michelle and Jeremy were incapable of lying clearly crossed the line of admissibility articulated in Haseltine. Carver's testi *390 mony "usurped" the jury's role as fact finder because the jury was no longer free to decide the credibility of Michelle and Jeremy.
¶ 19. In its closing argument, the State attempted to explain away Carver's testimony that Michelle and Jeremy were incapable of telling a lie. The State offered that while Michelle may be capable of creating a simple lie — for example, stаting that she had not had a sexual relationship with Tutlewski when in fact she had — she was not "capable of coming up with a lie and then describing it over and over again, describing a sexual assault." Adopting Carver's testimony, the State asserted that Michelle did not have the capacity to tell a "comрlex lie," that "Michelle and Jeremy . . . have all they can do to tell the truth," that Michelle was "not capable ... [of a] complex array of things that she would have had to relate again and again and consistently" and that she "simply [was] not capable of it any more than a small child is capаble of telling that kind of elaborate lie."
¶ 20. The State's explanation, however, cannot undo Carver's statement that Michelle and Jeremy were incapable of lying. The State, in fact, relied on this opinion in its concluding arguments.
When you put all of this evidence together, you have to conсlude one of two things. Either Michelle ... is lying about the whole incident or the defendant is, and Michelle simply isn't capable of that, and the defendant is. [Emphasis added.]
This assertion by the State, based on Carver's improper testimony, further infected the jury trial.
¶ 21. We are not convinced that the error in admitting Carver's opinion testimony was harmless.
*391
The test for harmless error is whether there is a reasonable possibility that the error contributed to the conviction.
See State v. Dyess,
¶ 22. Tutlewski's conviction came down to a credibility contest between Michelle and Tutlewski, the only eyewitnesses to the alleged sexual assault. The State maintained that Tutlewski had raped Michelle, but it presented no DNA or medical evidence connecting him to the sexual assault. Although Jeremy testified that Michelle had called him shortly after being raped, Michelle's testimony provided the substance of the sexual assault charge. Tutlewski, on the other hand, claimed that he had been having an affair with Michelle and that he had moved into Michelle and Jeremy's apartment to continue the affair. Tutlewski presented witnesses who testified that Michelle had fabricated the sexual assault charge to conceal their extramarital affair. As the State concedes, Tutlewski presented strong evidence that Michelle had lied about not having had a relationship with him. We must conclude, therefore, that the State's evidence was not so strong that it renders harmless the admissibility of Carver's opinion that Michelle and Jeremy could not lie. We also cannot say that there is no reasonable possibility that the improperly admitted evidence contributed to the verdict.
By the Court. — Judgments and order reversed and cause remanded.
Notes
See State v. Haseltine,
The State's reliance on
State v. Conley,
