The Office Interrogation
The Office Interrogation

William Dafoe plays Detective Donald Kimble as he interrogates Patrick Bateman about the disappearance of Paul Allen.

An interrogation is a type of discovery that detectives perform to gather facts about the case they are building. Without a lawyer present, most people will reveal incriminating information, even if they are not responsible for the crime being investigated. It's not really much of a cross-examination except when a detective asks a question that seeks a yes or no response.

By conducting a surprise interview in Patrick Bateman's office, Det. Kimble is taking advantage of his suspect. He's acting nice and gracious, to keep Patrick's guard down. He wants Patrick to tell him as much as possible while he's doing his investigation.

Patrick Bateman's Strategy

Did Patrick Bateman denigrate Paul Allen to cause Det. Kimble to care less about the disappearance of Paul Allen?

By revealing Paul Allen's drug use and sexual proclivities, Patrick demonstrated his detailed knowledge about Paul Allen. That might have backfired on him because it told Det. Kimble that Patrick knows Paul really well.

Suspicion

Did Det. Kimble already suspect Patrick Bateman in the disappearance of Paul Allen?

If Det. Kimble wasn't suspicious at the start of the interview, a good detective have sensed that something was up given Patrick Bateman's familiarity about Paul Allen's personal life. He went on to a

Here's an analysis by R Raffrody: