The Laughing Policeman (released in the UK as An Investigation of Murder) is a 1973 American neo-noir thriller film loosely based on the 1968 novel of the same name by Maj Sjöwall and Per Wahlöö.

Defying the orders of their police superior Lieutenant Steiner, they seek, find and smoke out Camarero, leading to a chase through the streets of San Francisco and a confrontation aboard another bus.

The direction is by Stuart Rosenberg, and marks a comeback of sorts... With The Laughing Policeman, he takes a labyrinthine plot and leads us through it at a gallop; he respects our intelligence and doesn't bother to throw in a lot of scenes where everything is explained.

[4]Variety praised the film, saying, "After an extremely overdone prolog of violent mass murder on a bus, The Laughing Policeman becomes a handsomely made manhunt actioner, starring Walter Matthau and Bruce Dern in excellent performances as two San Francisco detectives.

"[6] Matthew Hartman of High-Def Digest wrote that "[the film] could have been a great and gritty 70s thriller, unfortunately, it's [sic] primary story doesn't live up to the potential of the opening scene".