This is an interesting, and very detailed article on the techniques used these days by police to get confessions out of suspects. I believe the author is mostly referring to interrogations in the US, but in any case, it is rather interesting.
In looking for a replacement for illegal forms of coercion, police turned to fairly basic psychological techniques like the time-honored “good cop bad cop” routine, in which one detective browbeats the suspect and the other pretends to be looking out for him. People tend to trust and talk to someone they perceive as their protector. Another basic technique is maximization, in which the police try to scare the suspect into talking by telling him all of the horrible things he’ll face if he’s convicted of the crime in a court of law. Fear tends to make people talk. For a while, police tried such things as polygraphs to determine if the suspect was being deceptive, but polygraphs and polygraph training are expensive, and the results are almost never admissible in court. But some polygraph analysts, including a man named John Reid, began noticing that subjects exhibited certain outward, consistent physical signs that coincided with the polygraph’s determination of untruthfulness. Reid went on to develop a non-machine-based system of interrogation based on specific types of questions and answers that uncover weaknesses the interrogator can use against a suspect to obtain a confession. Reid’s “Nine Steps” of psychological manipulation is one of the most popular interrogation systems in the United States today.
See full article.