the interrogation and Doody's juvenile status, was voluntary:
Although the entire interrogation lasted approximately thirteen hours, Doody admitted he had borrowed Caratachea's rifle at the time of the temple murders after approximately two and one-half hours of questioning. Doody admitted he had participated in the temple robbery after approximately six and one-half hours of questioning, and his description of the events at the temple spanned nearly two hours
....
Although Doody characterizes the tone of the interrogation as coercive, the audio tapes reveal a courteous, almost pleading style of questioning during most of the interview. Each of the officers involved in the interrogation testified at the suppression hearing that Doody remained alert and responsive throughout the interrogation and did not appear overtired or distraught. Our review of the audio tapes confirmsof trying to exercise his right to remain silent in the precise fashion described earlier by the officers.[17] During the Miranda warnings, he was told: "You can be quiet if you, if you wish." But when Doody was quiet, the officers told him expressly that he had to answer themin other words, that he could not remain silent. Their refusal to stop questioning him reinforced these express statements. Indeed, Doody was explicitly told that the interrogation would continue until he confessed: "I'm gonna stay here until I get an answer." As a result, the officers' original warning informing Doody of his right to remain silent, itself a casual and underplayed message, was negated by their subsequent conduct, telling Doody he could not be silent, but rather that he