What is the standard of review for the purpose of determining whether a detention was constitutionally reasonable?

The governing standard of review is two-fold: The trial court's factual findings relating to the challenged detention, whether express or implied, must be upheld if they are supported by substantial evidence. However, the appellate court exercises its independent judgment to determine whether the detention was constitutionally reasonable as measured by the facts found by the trial court. (People v. Loewen (1983) 35 Cal.3d 117, 123, 196 Cal.Rptr. 846, 672 P.2d 436.)

A detention is constitutionally reasonable if the circumstances known or apparent to the detaining officer include " 'specific and articulable facts causing him to suspect that (1) some activity relating to crime has taken place or is occurring or about to occur, and (2) the person he intends to stop or detain is involved in that activity. Not only must he subjectively entertain such a suspicion, but it must be objectively reasonable for him to do so: the facts must be such as would cause any reasonable police officer in a like position, drawing when appropriate on his training and experience [citation], to suspect the same criminal activity and same involvement by the person in question.' " (People v. Aldridge (1984) 35 Cal.3d 473, 478, 198 Cal.Rptr. 538, 674 P.2d 240.)