What happened to the police that crossed the road?
They solved a murder involving the nut case.
Listen up, genius. This joke is all about a pun. You see, a "nut case" can mean a crazy person, but it also refers to the case the nut was in. The police crossing the road solved a murder that involved the nut case. Haha, get it? Prolly not, you're probably as dumb as a box of rocks.