Tag Archives: Sexual Assault

Sad teen crying

Conviction Reversed Because Expert Vouched for Accuser’s Credibility

The Iowa Court of Appeals recently held that a criminal defense attorney failed to represent his client effectively when he made no objection to an expert’s improper vouching for the credibility of a witness. The issue in Simpson v. State is one that arises frequently when experts testify for the prosecution in cases that allege the sexual assault of a child.

Expert’s Role

Experts for both sides can play important roles in a child sexual assault prosecution. In addition to medical and forensic experts who can help the jury understand physical evidence, experts often testify about the behavior of children. Depending on the facts of the case, a prosecution expert might testify about the reasons why some child victims delay reporting an assault, while a defense expert might testify about the reasons why some children make false reports.

When used by prosecutors, the expert testimony of a psychologist or social worker risks violating a defendant’s right to a fair trial if the expert does not stay within accepted testimonial boundaries that have been established by court decisions. When experts stray outside of those boundaries, the right to the effective assistance of defense counsel may be violated when the defense attorney fails to object to the improper expert testimony.

Some commentators suggest that it is unethical for an expert to suggest to a jury that a child witness is truthful because the training that experts receive makes them no more adept at detecting lies than anyone else. In addition, an expert should help the jury understand the evidence, but should not be an advocate for a particular side in a trial. Several convictions have recently been reversed because prosecution experts crossed the line between neutrality and advocacy.


In the Simpson case, the prosecution called Lana Herteen as an expert in “child sexual abuse dynamics.” Herteen testified about statistics suggesting that 86{d61575bddc780c1d4ab39ab904bf25755f3b8d1434703a303cf443ba00f43fa4} of adolescents who have been sexually assaulted do not report the assault right away, if ever. Those statistics are suspect (they assume that all the adolescents within that 86{d61575bddc780c1d4ab39ab904bf25755f3b8d1434703a303cf443ba00f43fa4} actually were sexually assaulted), but most courts allow expert testimony of that nature, subject to cross-examination and the testimony of rebuttal experts.

While noting that statistics about the percentage of alleged sexual assault victims who are telling the truth are not admissible, the court accepted that experts may generally testify about statistics concerning delayed reporting. The court noted, however, that those statistics cannot be viewed in a vacuum, and were part of the problematic nature of Herteen’s testimony.


Herteen described “grooming” behavior (the process of earning a child’s trust so that the child will later submit to sexual contact). She also testified about the sexualization of victims (by, for example, exposing them to pornography in order to make them comfortable with sexual discussions or activity).

Herteen crossed the line, according to the court, when her testimony moved from a generalized discussion of behaviors sometimes relied upon by abusers to the specific facts that the prosecution alleged to be true. An expert can say “here is how some abusers groom children,” but cannot say “here is now the defendant groomed this victim.”

The prosecutor elicited improper testimony by asking a series of hypothetical questions that referred to the specific facts of the case. By asking “would it be grooming if an abuser did X, Y, and Z?” after placing into evidence that the defendant had done X, Y, and Z, the prosecutor personalized Herteen’s testimony by making it clear that Herteen believed the defendant had groomed the alleged victim. That was for the jury, not Herteen, to decide.

In addition, “would it be grooming?” depends on the state of mind of the person engaging in the behavior. Expert witnesses cannot read minds and should not comment upon a defendant’s intent in committing specific acts. No amount of expertise entitles a witness to testify about what was in another person’s mind.


While most courts allow expert testimony about certain characteristics that have been repeatedly observed in child sexual assault victims, courts generally do not allow mental health experts to offer an opinion as to whether a particular child was abused. Nor do courts generally allow experts to express an opinion about whether a child is telling the truth. Courts usually agree that those issues are for the jury to decide, and that jurors may place too much value on the testimony of experts who are in no better position that the jury to decide whether a child’s report of a sexual assault was truthful.

In the Iowa case, Herteen testified about research that purports to show that teens who tell different versions of stories about being sexually assaulted will always maintain a “core of truth,” which she described as “the essence of the information” the teen is offering. In other words, if a teen consistently says “I was sexually assaulted” but repeatedly changes the details of the assault, the assertion that “I was sexually assaulted” should be regarded as the core fact that is truthful. That assumption has gained currency among prosecution experts despite the lack of any rigorous scientific evidence that the assumption is true.

Herteen also suggested that when child sexual assault victims are “coached” by their abusers, the story they were “coached” to say will eventually “fall apart,” revealing the “core truth” of the assault.

The court had little trouble concluding that Herteen’s testimony about “core truths” amounted to vouching for the credibility of the alleged victim. The court pointed to a long line of cases holding that it is improper for experts to make statements like “children don’t lie about important things,” not only because the testimony is demonstrably false, but because it is up to the jury, not the expert, to decide whether a child is telling the truth about being sexually assaulted.

The court also concluded that Herteen’s testimony about “coaching” the victim was a transparent attempt to bolster the alleged victim’s testimony by suggesting that children are incapable of lying over an extended period of time. Again, apart from the fact that kids are quite capable of maintaining a lie for years, it was improper for Herteen to suggest to the jury that the alleged victim’s story must be truthful because she would not otherwise have been able to continue telling it.

Conviction Reversed

The defense attorney failed to object to the improper testimony. The court of appeals concluded that that failure was inconsistent with the duty to represent a criminal defendant effectively. The court therefore reversed the conviction and ordered a new trial.

The lesson in this case for criminal defense attorneys is that they need to object when a prosecution expert crosses the line and becomes an advocate for the prosecution rather than an impartial expert. The lesson for experts is that they should not allow themselves to be led by prosecutors into overstepping that boundary.

Bill Cosby

Bill Cosby Uses Memory Expert to Challenge Accusers

Defending against charges that he sexually assaulted Andrea Constand in 2004, Bill Cosby’s lawyers have asked the trial judge to decide whether thirteen other accusers who might testify against him are competent to give testimony. Cosby’s lawyer is relying upon an expert witness to suggest that the memories of the witnesses are unreliable.

Charges Against Cosby

Constand reported the alleged assault in 2005, about a year after she claimed that Cosby fondled her without her consent. The district attorney at that time decided that there was insufficient credible evidence to justify filing charges.

Eleven years later, a new district attorney decided to prosecute the case. Cosby’s lawyer contends that the charges are politically motivated in light of the prosecutor’s campaign pledge to prosecute Cosby if elected. The charges came after other women made well-publicized accusations against Cosby of inappropriate sexual conduct.

Cosby’s own admissions might be the strongest evidence against him. After Constand sued him, Cosby admitted in a deposition that he touched Constand in a sexual way after giving her Benadryl when she complained about stress. Cosby also admitted that on other occasions he gave Quaaludes to women before he had sex with them. Cosby maintains that all of the sexual encounters were consensual.

Proposed Prior Acts Testimony

The rules of evidence in most states prohibit a prosecutor from introducing evidence that a defendant committed crimes in the past to prove that the defendant is probably guilty of the charged crime. The rule against “bad acts” evidence is meant to shield a defendant from prejudicial attacks on his or her character that might persuade a jury that the defendant deserves punishment for being a bad person, even if it isn’t clear that the defendant committed the charged offense.

The prohibition against “bad acts” evidence is, however, riddled with exceptions. The prosecutors in Cosby’s case want to call thirteen women as witnesses to testify that Cosby drugged them and then sexually assaulted them. The prosecutors are relying on an exception that allows prior acts to be used to prove that a defendant committed a crime in such a specific way that it constitutes the defendant’s “signature.” That exception usually applies when the identification of the person who committed the alleged crime is doubtful, which isn’t the case here, but the prosecutors nevertheless want to bolster their proof that Cosby assaulted Constand by proving that he previously assaulted thirteen other women in the same way.

Proposed Expert Testimony

Cosby’s attorneys filed an unusual motion asking the court to determine the competency of the thirteen women to testify about acts that Cosby allegedly committed between 1967 and 1996. The defense notes that none of those allegations were reported to the police and most were never mentioned to anyone until the recent media flurry concerning the alleged assault of Constand.

The motion alleges that most of the women did not consider themselves to have been victims of an assault until recently. Many of them have no recollection of any sexual contact occurring. The defense contends that the court should determine that the women are not competent to testify because their memories are unreliable.

The motion is unusual in that witnesses are normally presumed to be competent to testify unless they are very young children or suffer from a mental infirmity. As long as a mentally healthy adult witness has the capacity to observe events, recall those observations, and describe them in court, whether the witness is giving accurate testimony is usually for the jury to decide.

According to the motion, Dr. Elizabeth Loftus, a psychologist who is a leading expert in the field of memory, has reviewed the evidence and concluded that the memories of the thirteen witnesses have been “tainted in the decades since their alleged assaults occurred.” She bases that opinion on:

  • The length of time that has passed since the alleged assaults, which increases the probability that their memories are inaccurate.
  • The likelihood that extensive media coverage has tainted or supplanted the memories of the women who are now accusing Cosby.
  • The likelihood that the close interaction of the women has tainted their memories, as each fed upon and adopted stories told by the others.
  • Evidence of suggestive questioning by police and the media that tainted the memories of the witnesses.
  • Changes in the stories the women have told, which suggests that their memories have changed over time and are therefore unreliable.

A legal memorandum accompanying the motion suggests that the accusers have been encouraged to recall assaults that never happened by a “media frenzy.” Ten of the women are represented by the same lawyer, who in many cases facilitated media attention to publicize their accusations.

Cross-Examination or Exclusion?

In most cases, the reliability of a memory is challenged at trial by cross-examining the witness. Attacks on the reliability of a memory can also be bolstered by calling an expert witness to testify at trial.

It would be unusual for a judge to exclude eyewitness testimony on the ground that an adult, mentally healthy witness is not competent to testify, but this is an unusual case. The fact that the alleged assaults occurred decades ago and only surfaced after extensive media coverage of Constand’s allegations might push this case into uncharted territory.

It could also be true that Cosby’s lawyers expect the motion to be denied, but are hoping for a pretrial hearing that will provide an early opportunity to cross-examine the witnesses. That would give them a chance to preview their testimony and to impeach them at trial if they deviated from their pretrial testimony.

At this point, the judge has not decided whether any or all of the thirteen witnesses will be excluded from testifying under the “bad acts” rule. If the judge decides their testimony is not relevant, the competency motion will become moot. If some or all of the witnesses are permitted to testify at trial, it seems clear that Cosby’s lawyers will rely on expert testimony to challenge the accuracy of their testimony.

Photo Credit: By The World Affairs Council of Philadelphia [CC BY 2.0 (http://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons