The Skin Under the Claws (1975)

A series of brutal murders, the police on their toes, but they can not find a way to catch the sadistic murderer. A mad doctor experiments with ways to cheat death and confuse his pursuers with the help of a corpse identical DNA to his own. His young female victims are raped and brutally murdered with a knife. In the victims' fingernails will find the police traces of rotted human flesh.