Law & Order: Special Victims Unit: Season 3, Episode 6

Redemption

Detective Stabler is paired with John "Hawk" Hawkins (David Keith), an unstable, "cowboy" cop. They try to catch a serial rapist and murderer. Their suspect is a recently released prisoner, who was put in jail years ago due to Hawk. Alas, they come to deduce that not only is the predator someone else, but that the former prisoner is innocent of the previous murders, which means Hawk was responsible for putting an innocent man behind bars.