Nick Brown is the rapist of Jessica Walcott, a bar patron Brown stalked out of believing a "rape gene" made Brown commit the rape.
History[]
Brown's brother Mark was imprisoned for rape, so he joined an anonymous group led by Richard Witt focused toward the "rape gene" in hopes of curbing himself. When Brown was tracked, he offered selling out "The River Rapist", really a member of the group named Sam Dalton, at the next meeting and asked for a deal in exchange for getting Dalton to admit to raping three women.
Nick was brought to the group with a wire and tried to have Dalton confess when he arrived. Another member, Chris Perry, was unnerved by his questions, pulled a knife, and eventually found the wire. The group was raided, and Dalton was arrested. Nick was presumably found guilty of rape and imprisoned on a lesser sentence. (SVU: "Genes")