Ring of Death (1969) Romolo Guerrieri

In this Italian suspenser, a crooked detective begins investigating a situation on behalf of a friend and gets involved in murder, deception and double-cross.

A dialogue heavy murder mystery whose story is just full of twists and turns, "Un Detective", a.k.a. "Detective Belli", a.k.a. "Ring of Death", is a reasonably entertaining, competently made movie that does provide handsome leading man Franco Nero with a good vehicle, based upon the novel "Macchie Di Belletto" (translated as "Make Up Stains" in the English dubbed version) by Ludovico Dentice. He plays police commissioner Stefano Belli, a shamelessly crooked individual who takes a pair of cases offered to him by prominent criminal lawyer Fontana (Adolfo Celi). The details of these cases include a provocative photograph, blackmail, and cheating partners. 

Uncredited appearances are made by the likes of Laura Antonelli, Geoffrey Copleston, Silvia Dionisio, and John Stacy. But the most fun to be had is in watching Nero play a man of absolutely no moral fibre who always looks out for number one while becoming intent on solving the cases. He's a real brute of a man, yet is very democratic about it, roughing up men and women alike.