Officer Austin Bates is a dirty cop in the 31st Precinct under the employment of drug smuggler Nicky Farnesworth. Bates is the rapist and attempted murder of Sergeant Karen Smythe, the cadet instructor of Olivia Benson, to break her and try and silence her IAB investigation into his activities. The MO of suffocating her with a bag and choking her with a crowbar was ripped off from the rapist of Marina Garza to throw the investigation off track.
Bates was arrested with the other officers involved, Michael Towne and Murray. All three faced drug charges, except for Murray, who received immunity for testimony. Benson personally confronted Bates, the disgraced cop showing no remorse. However, to prevent Smythe's shame and endangerment, the rape charge never made it to trial. (SVU: "Paranoia")