From People v. Lowe, 130 Cal. Rptr. 2d 249 - Cal: Appellate Div., Superior 2002
Lacking California case authority on point, we are persuaded by the view of our sister states that speedometer readings may be introduced into evidence even without proof of the instrument's accuracy. The fact finder is then free to consider the lack of such proof in determining how much weight to afford the reading.
In light of the foregoing, we proceed to search the record for evidence supporting the conviction. Officer Lopez testified without objection that his speedometer showed appellant was traveling at 85 mph. He also testified the CHP periodically calibrates speedometers. Appellant offered no evidence showing, or even suggesting, that officer's speedometer was inaccurate. That instrument showed appellant moving at 15 mph over the maximum speed limit of 70. The court, as fact finder, was entitled to evaluate the likelihood that a speedometer in an official CHP vehicle would be inaccurate by such a large amount; evaluate the weight of the officer's testimony as to the speedometer reading in light of the lack of calibration results; and decide whether appellant was speeding. It did so and was convinced beyond a reasonable doubt appellant was guilty. We are bound by its factual determination.