US Supreme Court Howes v. Fields 10-680

Decision here.

   Fields was serving a sentence in a Michigan state prison for an offense unrelated to this case when sheriff's deputies wanted to question him about some sexual activity with a 12 year old boy which he had engaged in prior to his incarceration.  Fields was escorted away from the general population to an average sized conference room to meet with the deputies, who were armed.  Fields was told at least twice that he was free to return to his cell at any time, he was not handcuffed or restrained, and the door to the conference room was sometimes open and sometimes closed during the interrogation.  Fields was offered food at some point during the interrogation, which lasted between 5 and 7 hours.  Fields said at some point during the interrogation that he didn't want to talk to the deputies any more, but never asked to be returned to his cell (and the interrogation continued).  One of the deputies used a stern tone and profanity with Fields, at one point ordering him to sit down and telling him that if he didn't want to cooperate he could go back to his cell.  At no time during the interrogation was Fields ever given Miranda warnings.

   Fields eventually confessed, and the interrogation was ended.  Fields had to wait about 20 minutes for correctional officers to arrive and escort him back to his cell.  He was charged with and convicted of (insert name of applicable Michigan crime here), but his conviction was eventually overturned by the 6th Circuit, which held that his statement should have been suppressed.  The 6th Circuit held that being incarcerated creates a per se rule that a person is in custody for Miranda purposes, and needs to be advised of his rights.

   The US Supreme Court reversed the 6th Circuit, holding that being incarcerated for an unrelated offense does not mean that a suspect is in custody for Miranda purposes.  The court reasoned that "n: Questioning a person who is already in prison does not generally involve the shock that very often accompanies arrest; a prisoner is unlikely  to  be  lured  into  speaking  by  a longing for prompt release; and a prisoner knows that his questioners probably lack authority to affect the duration of his sentence.  Thus, service of a prison term, without more, is not enough to constitute Miranda custody."

   So there is no rule that an incarcerated person is automatically in custody under Miranda.  It depends on whether or not the circumstances of the interrogation itself would create the sort of coercive pressure that Miranda warnings are designed to prevent.  Also, the court recognizes that an incarcerated prisoner's sense of what is normal is going to be vastly different than an unincarcerated person, so the fact that the prisoner is not allowed to wander about freely (or otherwise violate prison rules) also has no bearing on whether the suspect is in custody.

   Related to this specific case, the court recognized that there were aspects of the interrogation which would support a finding that Fields was in custody (such as the length of the interrogation, the fact that the deputies were armed, and the stern tone used by one of the deputies).  Those factors were countered and outweighed by other circumstances, though (the door was left open sometimes, he was not restrained, he was offered food, the room was well it and comfortable, and especially that he was told repeatedly that he could return to his cell at any time).  Fields' conviction was upheld.