Expert witness for defense makes a (small) difference, study finds
The fiery debates surrounding the validity of actuarial tools to predict violence risk begs the question: How much influence do these instruments really have on legal decision-makers? The answer, at least when it comes to jurors in Sexually Violent Predator trials in Texas:
"Despite great academic emphasis on risk measures - and ongoing debates about the value, accuracy, and utility of risk-measure scores reported in SVP hearings - our findings suggest these risk measure scores may have little impact on jurors in actual SVP hearings."
The researchers surveyed 299 jurors at the end of 26 sexually violent predator trials. Unfortunately, they could not directly measure the relationship between risk scores and civil commitment decisions because, this being Texas, juries slam-dunked 25 out of 26 sex offenders, hanging in only one case (which ultimately ended in commitment after a retrial).
Instead of the ultimate legal outcome, the researchers had to rely on proxy outcome measures, including jurors' ratings of how dangerous an individual was (specifically, how likely he would be to commit a new sex offense within one year of release), and their assessment of how difficult it was to make a decision in their case.
There was no evidence that jurors' assessments of risk or decision difficulty varied based on respondents' scores on risk assessment tools, which in each case included the Static-99, MnSOST-R and the PCL-R. This finding, by the prolific team of Marcus Boccaccini, Daniel Murrie and colleagues, extends into the real world prior mock trial evidence that jurors in capital cases and other legal proceedings involving psychology experts are more heavily influenced by clinical than actuarial testimony.
What did make a difference to jurors was whether the defense called at least one witness, and in particular an expert witness. Overall, there was a huge imbalance in expert testimony, with almost all of the trials featuring two state experts, but only seven of 26 including even one expert called by the defense.
A back story here pertains to the jury pool in the Texas county in which civil commitment trials are held. All SVP trials take place in Montgomery County, a "very white community," an attorney there told me. A special e-juror selection process for SVP jurors whitens the jury pool even more, disproportionately eliminating Hispanics and African Americans. Meanwhile, many of those being referred for civil commitment are racial minorities. The potentially Unconstitutional race discrepancy is the basis for one of many current legal challenges to the SVP system in Texas.
Once a petition for civil commitment as a sexually violent predator is filed in Texas, the outcome is a fait accompli. Since the inception of the state's SVP law, only one jury has unanimously voted against civil commitment. Almost 300 men have been committed, and not a single one has been released.
Overall, the broad majority of jurors in the 26 SVP trials were of the opinion that respondents were likely to reoffend in the next year. Based on this heightened perception of risk, the researchers hypothesize that jurors may have found precise risk assessment ratings irrelevant because any risk was enough to justify civil commitment.
Risk scores could also be irrelevant to jurors motivated more by a desire for retribution than a genuine wish to protect the public, the researchers pointed out. "Although SVP laws are ostensibly designed to provide treatment and protect the public, experimental research suggests that many mock jurors make civil commitment decisions based more on retributive motives - that is, the desire to punish sexual offenses—than the utilitarian goal of protecting the public…. Jurors who adopt this mindset may spend little time thinking about risk-measure scores."
All this is not to say that actuarial scores are irrelevant. They are highly influential in the decisions that take place leading up to an SVP trial, including administrative referrals for full evaluations, the opinions of the evaluators themselves as to whether an offender meets civil commitment criteria, and decisions by prosecutors as to which cases to select for trial.
"But the influence of risk scores appears to end at the point when laypersons make decisions about civilly committing a select subgroup of sexual offenders," the researchers noted.
Bottom line: Once a petition for civil commitment as a sexually violent predator is filed in Texas, it's the end of the line. The juries are ultra-punitive, and the deck is stacked, with government experts outnumbering experts called by the defense in every case. It remains unclear to what extent these results might generalize to SVP proceedings in other states with less conservative jury pools and/or more balanced proceedings.
- The study, "Do Scores From Risk Measures Matter to Jurors?" by Marcus Boccaccini, Darrel Turner, Craig Henderson and Caroline Chevalier of Sam Houston State University and Daniel Murrie of the University of Virginia, is slated for publication in an upcoming issue of Psychology, Public Policy, and Law. To request a copy, email the lead researcher (HERE).