首先，你不能提前contest，应该按时间去回应。
其次，第一次出庭仅仅是plea guilty还是not guilty，如果你plea not guilty, 具体庭审要等再次安排。所以五月份那次去，你也没有机会辩解。第一次出庭警察不会去，要等到庭审的时候警察才会出面作证。
至于你的问题，你的根据是那个路口，没有限时左拐的标志，只有限时右拐的标志。而警察抓你的理由，“cannot turn into this street". 是假设左拐右拐都有限时。如果你证据确凿，你可以试一试。可能那天标志掉了，不是没有可能。
关键词是“beyond reasonable doubt”。 The police did not prove beyond reasonable doubt that I violated traffic control device. My pictures show that there was no traffic control device prohibiting left turn at the crossroad.
CA Vehicle Code
22101. (a) The Department of Transportation or local authorities in respect to highways under their respective jurisdictions, may cause official traffic control devices to be placed or erected within or adjacent to intersections to regulate or prohibit turning movements at such intersections. (b) When turning movements are required at an intersection notice of such requirement shall be given by erection of a sign, unless an additional clearly marked traffic lane is provided for the approach to the turning movement, in which event notice as applicable to such additional traffic lane shall be given by any official traffic control device. (c) When right- or left-hand turns are prohibited at an intersection notice of such prohibition shall be given by erection of a sign. (d) When official traffic control devices are placed as required in subdivisions (b) or (c), it shall be unlawful for any driver of a vehicle to disobey the directions of such official traffic control devices.
