Law & order SVU season 10 episode 12

In the 12th episode of the 10th season, a young 14 year old is discovered floating in the river. Cause of death was head trauma but her body was covered in scars and cigarettes burns. This brings them to discover that she was a very bright person that attended a special school. They meet the roommate who says that she would slip out at night dressed slutty. However this is proven to be a lie when another student advised them that the roommate was jealous of her. The father is arrested for abuse when the victims older sister tells Olivia about the way their father would punish them. However he is cleared of the murder. The roommate, while in interrogation, admits to trying to have a conversation with her that turned violent. Since the crime happened in New Jersey, she is to be trailed as an adult. Olivia tries to convince the DA not to do so, but later discovers that the girl was taking pills and staying awake days at a time. She is sentenced as a minor.  

Law & Order: SVU