Even though it’s typically up to the jury to decide what a reasonable person would have done, sometimes, the judge decides before the jury ever gets the chance. The court may decide that there is no dispute about the facts and that the defendant did not act unreasonably.
This kind of ruling is called summary judgment or summary disposition. It is rare, and the courts should only award summary disposition on the question of negligence in the clearest of cases. See Brown v. Martin Marietta Corp., 690 P.2d 889, 891 (Colo. App. 1984) for more details.