Key investigative tasks where psych is relevant: collecting and evaluating investigative info that is obtained from suspects during police interrogations, investigative decision-making, especially those requiring deep understanding of criminal behaviour. Some countries will convict only on confession but na, need other evidence too. Police interrogation - when police interview a suspect for purpose of gathering evidence and obtaining a confession - confession evidence the most potent weapon. Past - used physically coercive tactics to get a confession, like whipping, but now they use psych techniques such as lying about evidence, implying threats to loved ones. The mr. big technique - happens outside of the interrogation room; undercover pops pose and lure suspect into gang, must confess to a serious crime before sealing the deal w/mr. Big; they then use this confession against suspect in trial; not technically entrapment because the act was committed prior to operation but trying to put a stop to this.