Interrogation (also called questioning) generally means formally or informally interviewing a person to gain needed information of some kind. Interrogations are used by military organizations, intelligence agencies and law enforcement agencies worldwide. Sometimes the interrogated person is suspected of committing a crime or thought to have a reason to hide the information. The questioner in criminal and military interrogations is often an officer trained in different interrogation techniques. Depending on how they view the person being questioned or the purpose of the interrogation, the methods used may vary widely. For example:
The person being questioned may be a witness and may give information freely.
The person being interrogated may be suspected of a crime and the goal is a confession.
The person being questioned is not a suspect, but may not want to give any information.

Interrogation questions 
An interrogation may often begin with several closed-ended questions. Examples would be "are you comfortable" or "would you like a cigarette"? The intent is for the interviewer to control the conversation and put the person being interrogated at ease. Let them think they are not in any trouble.

Next may follow asking narrative questions to find out what the person knows about a subject. Next, the interrogator may ask direct questions. Throughout the interview interrogators may ask "cross-questions". These are the same question asked in different ways and at different times during the interview to see if the person being questioned answers them the same every time.

The Reid technique 
A method taught to police interrogators since the 1970s is called the Reid technique. It was named for a Chicago police officer who developed it in the 1940s. It is widely used in North America because it gets confessions; sometimes false confessions. It is based on outdated psychology that maintains if a person shows stress they are lying. Unfortunately most people show stress when in stressful conditions. Suspects are questioned, often by teams of police officers. The Good cop/bad cop routine seen on police procedural shows is an example of the Reid technique. The police use this method to convince a suspect that confessing to the crime (whether they are guilty or not) is the best way out for the suspect. Many false confessions have been obtained this way resulting in false inprisonments.

Informal questioning 
A police officer may stop and question a person at any time. They do not need to give a Miranda warning before informal questioning or before making an arrest. But any information gained this way is not admissible at a trial against the person. Miranda required advising a person of their rights before being question in police custody. If the person asks the officer if they are free to leave, they are not in custody. That is one of the few things a police officer may not lie about. During questioning police may use trickery, lying or other forms of deception in order to get a confession from a suspect.

PEACE method 
A fairly new technique is being used in the UK, Denmark, New Zealand and other places. The word PEACE is an acronym for Preparation and Planning, Engage and Explain, Account, Closure and Evaluate. It is considered a more ethical model of police questioning. It is intended to prevent wrongful convictions by eliminating any coercion or deceptive methods. When tested in England and Wales, it resulted in the same percentage of convictions as the older methods produced. Peace is more of a journalistic approach. It assumes a liar will find it increasingly difficult to keep all the lies consistent and will eventually break down and confess.

Third degree 
A historic method of obtaining confessions is the applying of the so-called third degree. It consists of treating a suspect brutally, keeping them awake for long periods of time with no food or water. Beatings were given along with threats. Often a suspect confessed to stop the abuse. The suspect was then forced to sign a paper saying he was not intimidated or coerced into giving his statement. In 1937, the court threw out a confession upon learning it was not given voluntarily but the defendant had been hung from a tree and whipped until he confessed.

Torture 
Even though it is a serious breach of most international agreements, torture is still used by some police, military and intelligence services. Torture is prohibited under international law, but it is still used. In 2014 the Senate Intelligence Committee found that the Central Intelligence Agency tortured terror suspects.

References 

Legal terms
Imprisonment and detention
Intelligence agencies
Human communication