Andy is concerned that his family’s history of violence will convince the jury that Jacob’s violent nature has overruled his excellent nurture, turning him into a killer. While Andy as the narrator focuses mostly on Jacob’s violence, he also leaves the reader to wonder whether he, too, has genetically inherited the tendency toward violence.

Andy grew up around violence until the age of five and lived his whole life knowing his father was a murderer. He discounts outright the idea that he has inherited any violent tendencies. Nonetheless, he hides his background from everyone in his life, including his wife. He knows that the very association with a murderous father might change the way people think of him. When Jacob is accused of murder, Andy is convinced it is not due to this violent nature and believes that his son is innocent.

Jonathan is able to exclude any evidence about a “murder gene” from Jacob’s trial. However, Billy, Andy, and Jacob all possess a gene associated with male antisocial behavior. The reader is left to determine to what extent this gene influences the three men’s behavior. Despite Andy’s assertion that he has never been violent, he displays a pattern of rule-breaking behavior, including obstructing justice in Jacob’s case, as well as threatening and harassing teenagers and suspects.