Steve Walker is a member of the swim team and the abusive boyfriend of Kim Garnet.
History
It was later discovered that Steve had been physically abusing her for months, though she kept this a secret from her friends and family, knowing that he would kill her if she told anyone. In 2009, she texted nude pictures of herself ("sexting") to Steve's phone (it's strongly implied that Steve forced her to take the pictures as well as send them). But, in the process, she accidentally sent a copy to her friend, Ethan Morse, who had a crush on her. Realizing this, she went to his house in Little Neck to explain things, but Steve followed her and thought she was cheating on him. In retaliation, he beat her up after she left Ethan's house and stole her cell phone.
Using it, he then sent copies of the pictures to several other students at school to humiliate Kimberly as well as keep her quiet. He also copied off his number to her own to make sure that no one would know that he sent them. Shortly thereafter, Kim fell down a flight of stairs at school, leaving her in a coma. Her doctor, Dr. Manning, noticed her previous injuries and called Detectives Elliot Stabler and Olivia Benson.
After learning of her texting the pictures to both Steve and Ethan, detectives suspected one of them of beating her. He was brought in for questioning but his father ended the interrogation when his son was accused of hurting Kimberly. In the hallway, Ethan and Steve got into a squabble: each accusing the other of beating Kim. Kimberly regains consciousness but refused to identify Steve as her abuser out of fear, simply saying that she fell.
Kimberly herself was then charged by Family Court Counselor Samantha Copeland with distribution of child pornography in order to coerce her into identifying her abuser, much to the anger of the SVU detectives, especially Olivia. However, Copeland's actions make Kim lose all trust the detectives had manage to gain from her and she refused to cooperate. The day before she was to appear in court, Steve beat her up again to keep her from naming him, breaking her arm in the process. Between the attack, Steve's threats and Copeland's continuing harassment, Kim completely shut down emotionally and remained silent in court about her attacker's identity. Judge Hilda Marsden then held her in contempt and put her in lock up for the night.
Fed up with Copeland's methods causing more harm than good, Olivia and Kimberly's Attorney, Miranda Pond, bring Elliot's daughter, Kathleen Stabler to speak with her. The three women encourage Kim, telling her that keeping quiet won't make her problems stop. Kathleen encourages her further, telling Kimberly about her own problems caused by her bipolar disorder as well as the realization that she would never be safe unless she took her life back.
With renewed confidence, Kim finally admits to the events, stating that Steve is the one who's been abusing her and the one who stole her cellphone, which led to the events with the pictures. With her testimony in place, Steve is arrested and is currently in prison. (SVU: "Crush")