Fallon's brain (on the right) has dark patches in the orbital cortex, the area just behind the eyes. This is the area that Fallon and other scientists say is involved with ethical behavior, moral decision-making and impulse control. The normal scan on the left is his son's. Courtesy of Jim Fallon hide caption

itoggle caption Courtesy of Jim Fallon

A machete that Bradley Waldroup used to wound his estranged wife. At right is the Bible Waldroup had been reading before his wife and her friend arrived at his home. Police crime scene image from the 10th District Police Department in Cleveland, TN hide caption

itoggle caption Police crime scene image from the 10th District Police Department in Cleveland, TN