How we change what others think, feel, believe and do
Show the person that there is only one thing that they can do, which is to give you the information you want.
Make them believe that there is no alternatives and no acceptable future unless they confess or otherwise provide you with the required information.
Allow them to feel good about conceding. Show them how this is not only necessary but also good and honorable. Praise them and show respect when they give you information.
I have given you time to think. The only choice left is to confess now.
Quick! Before Harry comes! Tell me now!
There is a true case of a man interrogated about the abuse of small children. He was humiliated by the police, who made him undress and ridiculed him during a long and intense interrogation, including threats to turn him over to the local neighborhood. He confessed. His treatment was later found not to be in violation of any law. (Wagenaar et al. 1993)
This method may only be used when the person is desperate and cannot face what will happen next. They must believe that punishment, humiliation or other intolerable future lies in front of them and that no other alternative course of action is available to them.
When faced with confession or psychic (or even physical) extinction, most people will choose confession.
Wagenaar, Willem A., van Koppen, Peter J. and Crombag, Hans F. M. (1993). Anchored Narratives: The Psychology of Criminal Evidence. Hertford, UK: Harvester Wheatsheaf.