Gretchen Corbett in An Exercise in Fatality (1974)

Milo Janus owns a chain of health clubs, but one of his franchisees discovers the man is cheating him–and can prove it to the authorities. Janus responds by murdering his partner and making it look as if he had accidentally killed himself trying to lift a barbell that was too heavy for him. Janus creates a would-be perfect alibi for himself involving a tape-recording of his victim’s voice, a phone that doesn’t light up, a sexy secretary, a party for friends at his house, and a pornographic horror movie. But no alibi is perfect when the rumpled Lt. Columbo is on the case.