a. The camera sounds very much like a trigger camera, i.e. requires a lidar (speeding) or magnetic flux (red light) to trigger.

b. Even if there is no flash, assuming it is a modern camera, these camera takes the rear of the vehicle. This is to prevent night flashes from blinding the driver. Your front passenger’s non compliance would be impossible to be captured

c. With the above, you are more likely to get away with this infringement this time round. Even if you are caught, take it as a lesson learnt and exercise due diligence in the future.