The game consists of 51 cards divided into 4 sets of 12 - Crime, Prosecution, Defense, and Alibi. There are three additional cards - the Prisoner and 2 Surprise Witness cards.
The game is essentially a trick-taking game with 3 of the sets. The Alibi set is not shuffled in, but acts as a scoring mechanism as players receive these cards for winning tricks. Witness cards act as trump cards.