Is this Berserk! with Joan Crawford? I recall Circus murders (with themes based on the acts), and spikes going through heads.
It came out in 1967, and was the very last movie to play in my home-town movie theater before it closed. You used to be able to walk downtown to the movies. But they had no parking lots, so they were done in by the bigger chain theaters.
Helluva flick to go out on. It was better to recall the last kiddie matinee flick – “A Dog of Flanders”