"Imagine a defendant who has been charged with murder, the intentional homicide of a victim he was robbing with a weapon. He has a history of three previous convictions and imprisonments for armed robbery. Prior to being released from the third term, he publicly threatened to kill any future armed robbery victims who might be able to identify him. When the current victim looked our armed robber in the eye, the robber said to the victim, "You looked the wrong way at the wrong guy," pulled the trigger, and killed the victim. (We know this because his accomplice has turned state's evidence and, unbeknownst to the robber, there was a witness who will corroborate the accomplice's evidence.) This is a desperate case. Assume that a lawyer has been assigned to defend the killer and she needs to discover evidence that will help her make an argument to defeat the charges against the defendant or that will help her seek mitigation at sentencing if the defendant is convicted. The lawyer is aware of the Caspi and colleagues (2002) study and its later replications that found a vastly increased risk for criminal behavior among males who had been subject to severe abuse as children and who had a genetic defect that caused an monoamine oxidase A (MAOA) deficiency. The lawyer is easily able to confirm from family members, teachers, and neighbors that the robber was severely abused as a child, and a genetic analysis confirms that the robber also has the specific defect associated with increased risk for crime..."