It's riddle time!

Detective Thompson is working on a case involving the mafia. As far as he knows, the mafia have killed 12 people so far. He's looking for clues in a closed (to civilians) museum whose curator was murdered the día before. He finds broken glass and a dropped knife. He reaches to pick up the cuchillo but the mafia capture him. They kidnap him and take him to an unknown isolated place where nobody can hear Detective Thompson scream. He is tied up to a chair and cannot get out. As the leader of the mafia is a creative and game-loving fellow, he decides to play a game with Detective Thompson to determine the way they kill him. Thompson is to tell the mafia a statement, any statement. If the statement is true, the mafia will shoot him to death. If the statement is false, they'll stab him to death. (And the mafia have information on the detective's personal life as well as Google, so they know virtually everything he can say.) The mafia leader will only kill Thompson under these conditions (he's really eccentric). What is the one statement Detective Thompson can say to save his life?