Matthew Van Aller was a detective with the 37th precinct who was also a murderer. He was a detective third grade.
History[]
Van Aller met with Stabler in the car and Van Aller writes down something on a notepad despite the fact that he has nerve damage. Van Aller then leaves the car but orders Stabler to stay inside the car as the men he is going to meet hasn't seen his face. Later, Van Aller drops Stabler off somewhere but Stabler insists on talking to him. Stabler gets Van Aller to trust him before bringing up the double homicide that the OCCB were investigating.
Van Aller confesses to the murders of a lawyer and her client, because the lawyer found out about The Brotherhood. After Stabler exits the car, Stabler enters a bar where he meets Tanisha Carling. Stabler then exits the bar and Carling follows him. Stabler then witnesses Van Aller commit suicide in the car which was also witnessed by Carling. (OC: "Guns & Roses")