OK, here is really why it happened....
First, we need to establsih the legal requirement as you approach a red light:
21453.
(a) A driver facing a steady circular red signal alone shall stop at a marked limit line, but if none, before entering the crosswalk on the near side of the intersection or, if none, then before entering the intersection, and shall remain stopped until an indication to proceed is shown, except as provided in subdivision (b).
So you must stop "
at" the limit line... Well, I think stopping "at" the limit line usually means cutting it too close where you might actually go over it or pass it which would make you in violation of 21453 but it can also be considered a violation of 21970 for blocking the crosswalk... So I think the wise thing to do is to stop BEFORE the limit line...
The system, believe it or not, is programmed to be a little more forgiving than what the law requires... How?
In cases where a driver might
slightly go over the limit line and although it is, by definition a violation, as long as you did not go through the intersection (whether to go straight, turn left or turn right) while the light is showing its red indication, the system is programmed to overlook that.
In your case, and based on your description, you
presumably stopped over or past the line, at which point the system is now programmed to wait you out to determine if you continued through (even if it was 5 seconds or so later) or whether you waited until a green indication is shown... You (I am guessing) did the former and went through...
How does it do this? two detector loops, one placed at the limit line and the other placed at the line marking the inside edge of the crosswalk.
Would such a citation stand even if there is no "No Turn On Red" sign? I mean you did stop... You were careful...
Yes, such a citation would in fact stand in spite of the fact that you stopped, waited 5 seconds or so during which you possibly checked cross traffic and pedestrians in the adjacent crosswalk and the proceeded with your turn... And yes, it would stand in spite of the fact the there is no "No Turn On Red" sign at that turn... It would stand because when you made your initial stop, you did so over or past the limit line, not at or just before it, which we've already established is a prohibited act!
Not much you can do at this point in time but worry and wait.
Red light camera citations must be issued and mailed to the registered owner of the vehicle at his/her address on file with the DMV within the 15 day period after the alleged violation.. So give it about 20 days or so... If you don't get anything, that means you got lucky and they decided not to issue a citation... In the meantime, if you have a job that allows for overtime or extra hours, you might want to do a few and start saving just in case.
Good luck!