Expert Testimony Timing Key To Prosecution of Bill Cosby

A key difference between the June 2017 mistrial in the prosecution of Bill Cosby and the April 2018 conviction was the timing of expert witness testimony. In the first trial, the sexual assault expert witness was put on the stand near the end; at the retrial, the assault expert was the first witness called.

In Commonwealth of Pennsylvania v. William Henry Cosby, Jr., some legal analysts have argued that the most important difference between the two trials was that only the primary accuser, Andrea Constand, and another woman were allowed to testify in the first trial, but at the retrial, five other women testified.

Yet, one juror, Harrison Snyder, said in an ABC interview that the additional women's testimony was not a major factor. Snyder was convinced to reach a guilty verdict by Cosby's deposition in which he admitted providing drugs to the women and the expert witness testifying that a victim's inconsistent statements and a delay in reporting an assault are normal.¹ Since the deposition was available in the first case, the expert witness testimony is left as the major difference between the trials.

That expert witness, forensic psychiatrist Barbara Ziv was the first on the stand for the prosecution at the second trial, spending 3½ hours testifying about the myths of rape: explaining that most perpetrators assault victims they know (85%), that while it may seem irrational to most people, these victims often stay in contact with the perpetrator (usually due to self-blame), and that their recollections are often inconsistent due to alcohol, drugs or the trauma of the event, and that they rarely file police reports immediately.

At the first trial, the defense challenged Constand on exactly those points: her contradictory statements to police, her multiple phone calls with Cosby after the alleged attack, falsely denying having been alone with Cosby before the attack — a long line of questioning that tried to frame Constand as young woman pulled into a romance with a man nearly old enough to be her grandfather.

Changing tactics somewhat at the retrial, the defense tried to paint Constand more as a money-grubbing schemer out for a big payday and as “a pathological liar.” The defense did though maintain its tactic of attacking the women for inconsistencies in their accounts, and their moral character. Notably, at the close of the trial, a defense attorney rhetorically questioned one of the victims: "Is there anybody she hasn't slept with?"

Those arguments did not win over the jury, in part perhaps due to Dr. Ziv's testimony which seems to have changed the jurors perspective before they heard from the victims and the cross-examinations by defense attorneys.

AS ABC Chief Legal Analyst Dan Abrams put it: “[I]t's a reminder that expert testimony does matter. This guy's making it clear that the expert who testified about what it means to be a victim mattered to him.”²

An expert witness who can set the jury's perspective before adversary council can begin to make its case has the opportunity to innoculate the jury to the opposing claims.

Cases such as these often boil down to “he said, she said,” but then few cases are won by simply letting the facts speak for themselves. Expert witnesses are storytellers, telling a factual story from their expert perspective. Getting the triar-of-fact to see the case from that perspective can depend not only on the story, but on when that story is told.