CounterIntelligence  
This is a notes from the great book "the Counter-intelligence" which was written by Orst Pento who worked for long years and during the second world war .
Note: the interrogations here differs greatly from the ordinary ones used by policemen because the spies are trained enough and smart that you can't prove anything against them and many of these ways are used by the case officers against their agents to be sure that they are still on their side and didn’t turn to be douple agent.
The properties of the counter intelligence officer:
1)Memory: because the officer not only has to remember faces or events or places he passes few years ago but also he has to remember all the details of the investigation without holding any pen because writing makes the investigation formal out of any rapport with the subject and also gives the subject enough time to arrange his thoughts and it will be more difficult to make him mistake.(now a days the recorders are used)
2)Patience and  loves the details: Every spy has a preplanned story to tell so you can never caught him in the broad line but you can caught unskilled spy mistaken in small details .
3)Languages: The officer must be perfect in several languages used because he will be tied if he doesn't know the subjects language or can't examine his papers even if he is a good investigator.
4)Practical psychology: In order to know the subjects personality in least time to decide the best way to deal with him, as some becomes stubborn when the investigator treat them with anger and threating but their resistance dissolves by kind words and flattering.
5)Boldness
6)Detailed knowledge about the wide geographical regions ,capitals , the cities and also the main & secondary streets , the buildings ,Hotels and the restaurants , the local properties and the distance between one point and another , all must be in his mind to use whenever he want.
7)The international law: because the officer can't keep the subject more than the defined time and he can scare his investigator that he deseves a protection under the international law so the officer must beat him in this field.
8)Must be a good actor: To pretend with anger or lost his patience  plus the practical psychology as it is a good thing to take a hard accent while the subject has normal voice and look or take the sympathy on him while he is hard and has sharp look , also the investigator must take care of his body language as well because the subject evaluate him also as he does.
9)The talent of deduction: The ability to discriminate between the reason and the result and the mental examination of the story. The honest person can tell unreasonable story or uncompleted in the first investigation as a result of emotions and also he can omit many details or important events due to confusion and real forgetting even the persons trained to tell whiteness omits important facts and tell the whiteness in wrong order so if someone tell a full neat story from the first time ,he must have studied it.
10)The investigator must know what he is looking for like cipher book or addresses or phone numbers and all the ways used to hide it .
Some ways of interrogation and taking confessions:
American : they depend on interrogation for a long times and using means like Sodium Pentothal & lie detector (see lie detectors section)............to be continued