Continuity mistake: Near the end of the film, as Aaron/Roy reveals his deception to Martin, notice the jail cell 'door' behind Martin. During the majority of the scene the door is closed, but in a couple of shots it is wide open.
Continuity mistake: In the scene in the bar when Martin is talking to the reporter and drinking, the napkin with the slice of lime on the counter in front of the liquor bottle moves from place to place in the shots, and to start with the reporter is on Martin's right (viewed from behind the bar) and then on his left (from the bar side).
Continuity mistake: At the beginning of the movie, Richard Gere's secretary ties his Bowie bowtie for him with the strap over his collar. He puts on his jacket, you can see the tie over the collar, they cut to a wider view, he steps out of the room and then returns immediately. He never reached up to his collar, yet the bow tie neck strap is under the coat of his shirt.
Continuity mistake: The videotape that Dr. Arrington shoots of Aaron differs from when he is actually talking to her in the scene as she records and when Martin Vail watches it at his home. It is clear that they were, at times, not the same. Example: Dr. Arrington, in the actual scene with Aaron, never asks Aaron what Linda did as work for Bishop Rushman but when Martin watches it at home, she does...a lot of other times too.
Answer: They knew he was a street kid and looked where the homeless and beggars hang out (under a bridge) they recognised him by his bandaged ear, from where the crucifix earring was ripped.