Gatso cameras are the fixed cameras on a pole that photograph your car against lines on the road as you allegedly break the speed limit. The camera box is usually yellow in colour and – as it is there to deter (and not simply to generate income!) – should be readily visible to you the motorist: at least that’s the theory.
They consist of a radar speed detection system and associated camera, with a flash, that takes two pictures of your car as it passes the detector at a pre-set speed or in excess of that speed. However, radar speed detection has some inherent inaccuracies (some of them still contain 35mm wet film!) and, therefore, you cannot be convicted on the evidence of the radar speed device alone. To secure a conviction the evidence from the radar must be corroborated by the photographic evidence of your car in the two photographs.
As the time between the two photographs is known, the speed of the car can be calculated by measuring the number of stripes on the road that it has passed. As distance divided by time equals speed it is fairly straightforward to work out the speed of your vehicle as it passed the camera. The time (a fraction of a second) taken is a known and recent legal authority supports the proposition that that time is something which is assumed to be correct. However, mistakes can, and do, occur. I do not propose to flag up the mistakes but you may think that using the services of an experienced motoring lawyer could pay dividends as, if a mistake is spotted by your lawyer, it can then be pointed out to the Crown Prosecution Service (CPS) who will may drop the case, or may be used in your court case to try and plant sufficient doubt in the minds of the Magistrates to force an acquittal.