"May I see the radar gun?"
Sure, it's right there mounted on the dash, see it?
"When was the last time this radar gun was calibrated?"
I'll be glad to present my calibration documentation in court on this date.
"Can you provide documentation showing when this radar gun was last calibrated?"
I just answered that.
"Are you aware that the margin of error for even a calibrated radar gun can be as much as 4 miles per hour?
Are you aware that it can be more than that if I shoot your car at a 90 degree angle and it's always going to be in your favor?
"Did you know the margin of error for a speedometer is approximately 5 miles per hour?"
When was the last time you had your speedometer calibrated? Can you provide documentation showing the last time it was calibrated?