One of the most rewarding aspects of the work back in the day was pulling a confession out of a reluctant to give it up criminal who thought he was clever enough that he could lie and outsmart his interrogator. They never quite proved up to that task and would dig themselves deeper with each false statement and the inability to keep track of the their lies.
Outwitting them and using their own words to break down their stories prevented the use of more traditional lie detection methods...