Frank Minnelli is a detective in the NPD. April first encounters him outside the Mercury Theatre, where he is waiting for Cortez. She criticises his dress sense and uses a piece of candy from the Fringe Cafe dipped in some sort of kerosene-smelling goo to make him leave his post. Unlike most Newport street cops who wear exoskeletal armoured suits, Minnelli is an old school detective who dresses in a trenchcoat and a fedora. He is also a compulsive eater who enjoys fast-food from Kool Kow, especially fries 'soaking in melted goat cheese'. However, he doesn't need to leave his post because his bowels are genetically enhanced. Minnelli also has a synthetic eye, though the history behind this is never explained.
April meets Minnelli again at the Newport police station in the Locker Room, where he's stuck in the toilets, suffering the effects of her 'poisoning'. He keeps a bottle of stomach medicine in his locker, which suggests that Minnelli's 'enhanced bowels' mean he has a sensitive stomach. From what Minnelli says, it's hinted that although he's married to Laura Minnelli, he has had an affair with Sgt Maria Hernandez, who April impersonates to get Minelli's password (his wife's birthday).
Gordon Halloway complains about Minnelli to April later on in the story, making it sound as if Minnelli was in the Vanguard's employ ("He has proven useful in the past"), and it must be remembered that he was following Cortez. However, Jacob McAllen tells April he 'owns' Newport, including the police, so it's likely Gordon was referring to the police in general. They tortured Minnelli for 8 hours to extract information about April, although he knew nothing useful. Gordon says that they had to alter his memories, and adds that they removed "few...unfortunate childhood memories" while they were at it, implying that Minnelli was abused as a child.
Frank Minelli is voiced by Madison Arnold and is noted for his Brooklyn accent. His personality is based on the protagonist of the 1970s cop series Columbo.