The Laughing Policeman (1973) is an American police procedural film loosely based on the novel The Laughing Policeman by Sjöwall and Wahlöö. The setting of the story is transplanted from Stockholm to San Francisco. It was directed by Stuart Rosenberg and features Walter Matthau as Detective Jake Martin (the literary Martin Beck).
A busload of passengers, including off-duty police detective Dave Evans, is gunned down and killed. Evans, on his own time, has been following a man named Gus Niles in search of information linking businessman Henry Camarero to the murder of his wife, Teresa, two years earlier.
Evans was the partner of Detective Sergeant Jake Martin, a veteran but cynical member of the Homicide Detail working the bus massacre investigation. Jake originally investigated the Teresa Camarero case and been obsessed with his failure to "make" Camarero for the murder. Jake returns to it after many dead-end leads in the bus investigation. Niles was killed on the bus as well, and it was Niles who provided the alibi that enabled Camarero to cover up his wife's murder.
The sullen Jake and enthusiastic but impulsive Inspector Leo Larsen are paired to interview suspects. Jake shuts