S4, E21: When a female party-goer (guest star Katherine Moennig) defends herself after being sexually assaulted, killing her attacker, Detectives Benson (Mariska Hargitay) and Stabler (Christopher Meloni) attempt to support the girl's claim of self-defense. However, when DNA evidence uncovers the girl is really a man, the detectives begin to question the validity of the victim's defense.