Immediately, [defense attorney Wylie] Richardson went to forensic psychiatrist William Bernet of Vanderbilt University and asked him to give Waldroup a psychiatric evaluation. Bernet also took a blood sample and brought it to Vanderbilt’s Molecular Genetics Laboratory. Since 2004, Bernet and laboratory director Cindy Vnencak-Jones have been analyzing the DNA of people like Waldroup.
They’ve tested some 30 criminal defendants, most of whom were charged with murder. They were looking for a particular variant of the MAO-A gene ”” also known as the warrior gene because it has been associated with violence. Bernet says they found that Waldroup has the high-risk version of the gene.
“His genetic makeup, combined with his history of child abuse, together created a vulnerability that he would be a violent adult,” Bernet explains.
Over the fierce opposition of prosecutors, the judge allowed Bernet to testify in court that these two factors help explain why Waldroup snapped that murderous night.
“We didn’t say these things made him become violent, but they certainly constituted a risk factor or a vulnerability,” Bernet says.