Giallo a Venezia (1979)

In Venice a detective is on the trail of a killer who commits a double murder (a married couple) then more grisly killings occur. Sex, drugs, gore and perversions are ingredients of this sadistic and sleazy giallo.

From Imdb:
“Giallo a Venezia” is,without a doubt,one of the sleaziest movies ever produced in Italy.Along with “The New York Ripper”(1982,Lucio Fulci)and “The Killer Is Still Among Us”(1985,Camillo Teti)this is possibly the nastiest giallo ever made.The film begins with a double murder on the Venetian docks:architect Fabio(Gianni Dei)is stabbed with a pair of scissors,while his wife Flavia(Leonora Fani)is drowned.The fact that Flavia was pulled back from the water by the killer after being drowned,intrigues inspector DePaul(Jeff Blynn)and his assistant Maestrin.As they begin investigating friends of the couple,such as Marizia(Mariangela Giordano from “Burial Ground” and “Malabimba”),they soon discover that Fabio was in fact a sex crazed cocaine addict,who could only achieve sexual gratification by violence and sick voyeurism put upon his wife.During the investigation Marizia begins to receive threatening phone calls from ex-lover and soon after that a series of brutal murders is set in motion.

Alternate Titles
Gore in Venice