Michael Thatcher is a rapist of two women arrested and interrogated by Stabler and Benson. Both of them were cornering Thatcher to break his overconfidence in hopes of enraging him into confessing, by tactics such as calling him impotent and playing off his misogyny. Benson was pulled out under obligation before Thatcher could confess.
Benson later had another go at interrogating Thatcher in hopes of a confession, but she was furious about the legal bind she was in that pulled her out in the first place. She was bitter and angry, so she took it out on Thatcher, first by hitting him upside his head, then knocking him out of the chair and repeatedly kicking him. Thatcher confessed, but the brutality made it inadmissable.
Cragen later revealed Thatcher was convicted for the rapes based on confirmation with physical evidence. (SVU: "Florida")