An innocent prisoner will become more angry by the hour due to the injustice suffered. He will shout and rage. A guilty prisoner becomes more calm and quiet. Or he cries. He knows he’s there for a reason. The best way to establish guilt or innocence is non-stop interrogation.
First thing on the job, you know what I learned? How to spot a murderer. Let’s say you arrest three guys for the same killing. You put them all in jail overnight. The next morning, whoever’s sleeping is your man. You see, if you’re guilty, you know you’re caught, you get some rest, you let your guard down.