What is the test for a motion to suppress evidence?

In reviewing the denial of a motion to suppress evidence, the "trial court's factual findings relating to the challenged search or seizure, 'whether express or implied, must be upheld if they are supported by substantial evidence.' [Citation.]" (People v. Loewen (1983) 35 Cal.3d 117, 123, 196 Cal.Rptr. 846, 672 P.2d 436.) Nevertheless, the appellate court exercises its independent judgment to measure the facts, as found by the trial court, against the constitutional standard of reasonableness. (People v. Leyba (1981) 29 Cal.3d 591, 596-597, 174 Cal.Rptr. 867, 629 P.2d 961.)

An appellate court is to review the record only to determine if substantial evidence supports the conclusion of the officer that the defendant had committed a crime. It must then exercise its independent judgment to decide whether the officer's subjective belief was objectively reasonable under the Constitution. (People v. Gabriel (1986) 188 Cal.App.3d 1261, 1265, 233 Cal.Rptr. 769.)