What is the actual duration of a police interview for which the parties agree the questioning lasted for over 3 hours?

While the parties agree the questioning lasted "for over three hours," the transcript indicates it was only slightly over two hours in length. One detective noted the time as 8:14 p.m. when the interrogation began. After it ended, the detectives obtained defendant's DNA sample, noting the time as "2221," i.e., 10:21 p.m. In any event, defendant fails to present any authority that a three and one-half hour interrogation rendered his confession involuntary as a matter of law. (Berghuis v. Thomkins (2010) 560 U.S. 370, 387 [130 S.Ct. 2250, 176 L.Ed.2d 1098] [three hour interrogation while sitting in straight-backed chair; "there is no authority for the proposition that an interrogation of this length is inherently coercive"].)