Visible crew/equipment: In the scene after Patrick Bateman's second encounter with the detective in his office, we see Bateman having sex at Courtney's apartment. After he rolls off her, Bateman approaches the large, stand-up mirror in the bedroom. In the upper right hand corner of the mirror, a boom microphone can clearly be seen moving around to pick up Christian Bale's lines. The next time we get the same long shot, the microphone is gone. (00:52:45)
Visible crew/equipment: In the opening scene, the camera and camera man can be seen reflected in the knife.
Visible crew/equipment: In the office scene when Kimball is talking with Bateman, a microphone boom can be seen in the CD's reflection behind Bateman.
Visible crew/equipment: In the scene where Patrick Bateman is walking the streets, just before that encounter with the lady who is waiting for the red light to change, you can see the camera crew reflected on the store windows.
Visible crew/equipment: After the beginning of the movie where there is an aerial shot of New York City just before we see Patrick getting at his office, the filming helicopter can be briefly seen reflected on one of the buildings' glass on the left side of the screen while it films the scene. (00:07:13)
Visible crew/equipment: When Patrick is at the dry cleaners, and arguing with the owners, a woman called Victoria comes in and offers to get Patrick's clothes cleaned for him. Just before Patrick leaves he says "Oh boy, I've got to go. Thank you, Victoria" and you can see the boom microphone reflected in the glass door (just above Victoria's head). (00:14:17)
Visible crew/equipment: The first time Patrick Bateman enters his office (listening to "Walking on sunshine") you can see a boom microphone reflected in the glass partition of his secretary's office area. (00:07:44)
Visible crew/equipment: When Patrick brings Sabrina into his apartment for a threesome with Christie, he says to her "Not quite blonde, are you?" and you can see the shadow of the boom microphone fall across the wall. (00:40:19)
Visible crew/equipment: When Patrick Bateman is showing Detective Kimball out of his office, the boom microphone can be seen poking into the shot on the other side of Bateman's interior office window. (00:36:46)
Answer: The situation is intentionally left vague. The homeless man being murdered wouldn't necessarily make the news in the time (there were over 4000 murders in 1989-90 when the book and movie are set). He and his friends are so alike that they continually mistake each other for others. The prostitutes would likely be loathe to call the police because they might be arrested themselves and he would likely get off with a much better lawyer.
Greg Dwyer