It is a simple question. You can first tell examiner the reasons why interrogation is conducted in the introduction. To find two things:- (i) componenets of a crime and (ii) identifying , locating and proving the guilt of the guilty party. You can tell him that crime has two components named Actus reus which means physical manifestation of crime and Mens rea which means the intent.
After ths you write about techniques like i told him about The Reid Technique and The PEACE method. Reid has further three components ; factual analysis , behavioral analysis interview and interrogation. Thn each component is divided into many others. After reid explain PEACE and thn conclude the answer.
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