Visible crew/equipment: As the camera pans down from the light in the mausoleums at the start, look at the door and you can see the camera shadow moving downwards. (00:06:00)
Visible crew/equipment: Several times in the movie you can see a stunt double for Donnie Wahlberg, like when he tries to hang himself. Art runs over and there is a wide shot focusing on both of them. No slo-mo required, but you can see it's a stunt double.
Visible crew/equipment: As Jill is being interrogated, when it cuts to a shot where the two cops are looking at her through two way glass, a camera man is visible between them and the boom mic is seen at the top left hand corner, very faintly.
Answer: Realistically there is no way he could have known. The writers were just working backwards from the plot point on this one.
Phaneron ★