Illinois v. Perkins

The Miranda doctrine must be strictly enforced, but only in situations where the concerns underlying that decision are present (i.e., a government-dominated atmosphere whereby the suspect may feel compelled to speak by the fear of reprisal or in the hope of more lenient treatment should he confess). That coercive atmosphere is not present when an incarcerated person speaks freely to someone whom he believes to be a fellow inmate. In such circumstances, Miranda does not forbid mere strategic deception by taking advantage of a suspect’s misplaced trust. The Miranda warnings were not meant to protect suspects from boasting about their criminal activities in front of persons whom they believe to be their cellmates. Note that Massiah v. United States, which held that the government could not use an undercover agent to circumvent the Sixth Amendment right to counsel once a suspect has been charged, is inapplicable here since no murder charges had been filed at the time of the interrogation (the Sixth Amendment had not attached).

Coercion is determined from the perspective of the suspect. The inherent coerciveness of custodial interrogation is not present when the target is unaware that he is talking with authorities. Miranda is not concerned with ploys to mislead a suspect or lull him into a false sense of security that do not rise to the level of compulsion or coercion to speak.