How we change what others think, feel, believe and do
Show sympathy for the other person and their situation.
Legitimize what they may have done or said by showing how you understand them.
Offer them mitigating arguments that they can use to excuse themselves.
Carol, I can really understand why you would do that. I've been in similar situations myself and felt like doing it myself.
Look, you were only doing your job, I know. It's not glamorous but somebody's got to do it, haven't they?
Interrogators will often play the concerned friend in order to get the other person to confess. It is fairly well known that soft and sympathetic approaches are often more effective at getting confessions and other information.
Sympathy may also be alternated with extreme pressure, perhaps with different people taking different roles.
If the person being interrogated has been trained in counter-interrogation, then sympathy will be very unlikely to work.
Sear and Williamson (1999) described these two themes thus:
Sear, L. and Williamson, T. (1999). British and American interrogation strategies, in D. Canter and I. Alison (eds) Interviewing and deception, Aldershot: Ashgate