Anthony Kennedy

“ United States, 377 U.S. 201, 206, 84 S.Ct. 1199, 1203, 12 L.Ed.2d 246 (1964) (holding, in the context of the Sixth Amendment, that defendant's constitutional privilege against self-incrimination was "more seriously imposed upon . . . because he did not even know that he was under interrogation by a government agent") (citation and internal quotation marks omitted) .
Custody works to the State's advantage in obtaining incriminating information. The psychological pressures inherent in confinement increase the suspect's anxiety, making him likely to seek relief by talking with others. ”

“ Similarly, where the suspect is incarcerated, the constant threat of physical danger peculiar to the prison environment may make him demonstrate his toughness to other inmates by recounting or inventing past violent acts. ”

“ In rejecting that conclusion, the Court finds that "conversations" between undercover agents and suspects are devoid of the coercion inherent in station house interrogations conducted by law enforcement officials who openly represent the State. Ante, at 296. Miranda was not, however, concerned solely with police coercion. It dealt with any police tactics that may operate to compel a suspect in custody to make incriminating statements without full awareness of his constitutional rights. ”

“ Ante, at 299-300. Perhaps this prediction is true with respect to fact patterns virtually identical to the one before the Court today. But the outer boundaries of the exception created by the Court are by no means clear. ”