1 mph over is ridiculous the margin of error in the speed gun is probably greater than that
I have heard of stories where someone got a BS ticket for something like 5 mph over and they challenged the ticket in court and asked for the calibration records on the speed gun. If it was not recently calibrated that 5 mph can possibly fall within the margin of error. My father in law has been pulled over by the DOT during harvest season for possibly being over weight with his grain truck. They make you drive your rear axle over a portable scale. He'll ask the officer to follow him to where he is hauling his load and compare the weight he got with what they get on their scale because the grain elevator scale is usually checked much more often than their portable scale is and many times the weights will be off enough he is able to avoid a ticket when the grain elevator's weight is within range of the weight limit. That is a point of sale so you can bet that it is going to be checked regularly because if it is off that is going to affect someone's profit margins.