Wow, that was an awesome bad movie. Notes:
1) The opening scene depictions of gay leather clubs are great. It's so authentic that William Friedkin didn't even have the dudes dancing in jockstraps shave their asses. Seriously, you frequently see unattractive, hairy asses in this movie.
2) In New York circa 1980, about 66% of all gay men into leather apparently got their hair advice from Lou Reed. Most of the remainder got it from Freddie Mercury. Everyone's dress style is totally Tom of Finland, though.
3) Jesus, this movie is a plotting disaster. You can't tell what the fuck the intent of Al Pacino's "inner struggle" was. I mean, I assume he's supposed to be questioning his sexuality as he gets deeper into the scene, but it's not consistent at all.
4) Similar plot disaster: The gay serial killer happens to be doing his thesis on the ORIGINS OF AMERICAN MUSICAL THEATRE.
5) I like how all the gay clubs are playing filthy, garage-y rock. I don't know who did the soundtrack, but a lot of it is very Stooges-y.
6) Making a suspect masturbate in front of 4 cops to get a semen sample. That's what I'd actually consider good plotting.
7) Fisting scene, featuring snappy editing!
Anyway, 9/10. It's a pretty fucking ridiculous movie. And it's streaming on netflix! See Al Pacino play gay, yet somehow be less flamboyant than Tony Montana.