David Goldstein from CBS Los Angeles recently investigated a Beverly Hills red light camera possibly violating state law. According to his report, the traffic control signal located on the corner of Wilshire and Whittier had a yellow light interval time of 3.0 seconds. (You can view how they timed the light here.) According to California Vehicle Code Section 21455.7, intersections equipped with red light cameras must meet the minimum yellow light interval established by the Department of Transportation and according to the Department of Transportation ,a yellow light interval time for the posted speed limit in that intersection (30 mph) would be 3.2 seconds. 
Of course if you’re the city, you’d argue the news investigation didn’t properly time the yellow light. Thus, the .02 discrepancy would be a result of other factors like human error when they recorded their observations.
The issue, however, wouldn’t be the difference between 3.0 seconds and the mandatory minimum 3.2 seconds. The crux of the matter would be the difference between 3.0 seconds and the time listed by the camera. Let’s say motorists received tickets the same day this investigation occurred. On the day of their trial or perhaps earlier when they receive their ticket, they will know exactly how long the city asserts the duration of the yellow light. If the city says the yellow light was on for 3.4 seconds then the discrepancy would be that much greater. Such a difference would make it more difficult for the city to account for human error or some other random explanation. In effect, not only would this evidence mean the city is violating state law but also the reliability and accuracy of these red light cameras would be questionable. Those extra tenths of a second can mean the difference between lawfully or unlawfully entering the intersection before the red light.
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 CVC 21455.7 Automated Enforcement Systems: Minimum Yellow Light Change Interval
(a) At an intersection at which there is an automated enforcement system in operation, the minimum yellow light change interval shall be established in accordance with the Traffic Manual of the Department of Transportation.
(b) For purposes of subdivision (a), the minimum yellow light change intervals relating to designated approach speeds provided in the Traffic Manual of the Department of Transportation are mandatory minimum yellow light intervals.
(c) A yellow light change interval may exceed the minimum interval established pursuant to subdivision (a).