In Crooks v. Pirrone (1964) 228 Cal. App. 2d 549, the trial court did not abuse its discretion in finding the officer not qualified to opine as to a driver's unobserved speed after the officer "admitted that he had never taken the course given by the California Highway Patrol at Sacramento for the ascertainment of speed from the physical results of a collision; there was no showing that he had ever personally conducted experiments along this line or that his conclusions relative to speed in other cases had ever been verified; neither is there anything in the record to indicate that the officer knew sufficient facts concerning the type and weight of the vehicles involved or of principles of mechanics or physics to permit him, as an expert, to arrive at any reasonably accurate opinion as to the speed of the respective vehicles." ( Id. at p. 553)