Autopsies of decomposed bodies are shown in close up of genital areas; nothing specific can be identified. A couple is seen from a distance having a having sex in a car; we see policeman's sketch of the activity.
There is a lot of talk about how the murderer sexually abused his victims before and/or after they were murdered. There is also talk about how he masturbated while killing them, often achieving orgasm.
There is a scene showing the murderer having sexual relations with his wife, although no nudity is visible. The wife expresses her dissatisfaction at his performance.
A man has sex in the woods with a woman who is not his wife. He is shown on top of her; no nudity. But he is not able to achieve penetration.
A man is told to remove his clothes for a strip search. Nudity includes bare chest and and bare buttocks.