What is the test for whether a reasonable person would conclude that they were free to leave while being questioned by the police?

The issue raised by these cases concerns when a court and when a fact-finder should determine whether a reasonable person would conclude that he or she was free to leave while being questioned by the police. In United States v. Montilla, 928 F.2d 583, 588 (2d Cir. 1991), we indicated that "freedom to leave" was generally a legal question to be decided by a court. In Posr v. Doherty, 944 F.2d 91, 99-100 (2d Cir. 1991), we suggested, instead, that it was usually a fact issue for the jury. The revised panel opinion says that, actually, the question is a mixed one of law and fact. See 221 F.3d at 340 ("Whether a seizure occurred is a question of law to be reviewed de novo, while the factual findings underlying that determination are reviewed for clear error."). Fair enough. But that statement does not explain whether the reasonableness of a questioned person's belief as to his or her freedom to leave is one of the underlying factual findings or is, instead, part of the legal conclusion.