Child abuse is discussed in a few episodes. In one of the late seasons, a character's traumatic childhood is revealed, and someone taunts him about not doing something to help his sister when they were children and she was sexually abused.
Torture is fairly frequent. It is usually shown just offscreen, but it is clearly brutal. It is often narrated and screams, drilling noises, etc are heard, and blood spatter is sometimes shown. One of the members of the team has a past as an interrogator and he frequently mentions how much he enjoys torture, even though he doesn't want to.