Can a citizen informer who sees a uniformed officer in a marked car be considered a witness to a crime?

It is well established that citizen informants who are witnesses to a criminal act are presumptively reliable unless the circumstances cast doubt on their information (People v. Ramey (1976) 16 Cal.3d 263, 269, 127 Cal.Rptr. 629, 545 P.2d 1333), and that in certain circumstances an inference of unlawful activity may be drawn where a person who sees a uniformed officer in a marked car attempts to avoid the officer (People v. Huntsman (1984) 152 Cal.App.3d 1073, 1091, 200 Cal.Rptr. 89).