In 2006, Bradley Waldroup, who lived in a trailer home in the mountains of Tennessee, USA, got into a violent argument with his wife and her female friend, as he believed they were having an affair. In a sudden escalation of violence, he shot and killed his wife’s friend, shot his wife in the back as she tried to flee, then dragged her inside and cut her with a knife and a machete, before she was saved by the intervention of the police. Waldroup was charged with first-degree murder, attempted first-degree murder and aggravated kidnap. During the penalty phase of the trial, the defence team introduced expert genetic testimony, seemingly without any objection from the court, citing data that was generally well accepted at the time (but now no longer accepted) claiming that a particular genetic variant contributed to aggression. The defence argued that Waldroup was not able to act as a ‘reasonable man’ might have acted in the same situation due to his genetic predisposition, making the act less volitional. The jury proved receptive to this argument.