How much influence do forensic psychologists have on trial outcomes?
Not as much as we'd like, two prominent psychologists assert.
In one study, David Shapiro found that psychological testimony about a defendant's mental illness did not reduce the likelihood of a jury imposing a death sentence. Paradoxically, instead of feeling sympathy for the defendant, judges and juries may perceive mental illness as a threat warranting execution, Shapiro said.
An exception, he found, was testimony regarding prior abuse suffered by the defendant, which may create sympathy and understanding.
At the recent APA convention in San Francisco, psychologist Lenore Walker reported a similar pattern in child custody cases.
According to Walker, judges often ignore psychologists' testimony about who should get custody in high-conflict divorces, trusting their gut feelings over the opinions of experts.
The discounting of expert psychologists is especially likely, both psychologists agreed, in cases of dueling experts. Jurors and judges may have trouble weighing the competing evidence and so just discount all of it.
The psychologists called for greater outreach to courts regarding the potential utility of expert testimony, and how to differentiate good expert evidence from bad.
The full story, in the current issue of the American Psychological Association's news magazine, is available online.