Wow, I get to use this line twice in one day!
Retired LEO Officer (25+ years) here that was assigned to Highway Patrol...
In the county I worked in, and in New York State, there was a safeguard built into the speed detection process to benefit the motorist.
First, I had to be certified in the use of Radar/Laser. That certification was my license to transmit radar and laser waves accurately for a legitimate purpose. Try transmitting (jamming) near sensitive areas, and you get to meet some alphabet government agencies.
Second, the observing/issuing officer had to do an "independent estimation of speed" before using laser/radar. Your estimate had to be within 5 miles an hour.
A summons could be written based upon that estimate alone. So if I estimated 65 in my head, and the radar/your speed read 60, I could write a summons for 60. If my estimate was 66, I would not write the summons. If you were speeding in my estimate, but I could not get a radar/laser reading, you still were stopped regardless of radar absorbing paint or jamming equipment.
With that in mind, we were trained to not use laser detection through a window as it may distort the signal. Therefore when using laser, I was
always perpendicular to the roadway I was targeting (with the window down). Combine this with time needed for independent estimation of speed, most of the summons were issued between 800-1200 feet. (The laser gun would also give you the distance the speed was measured at.)
Think about it for a minute. Most patrol vehicles have very reflective lettering/department crest on the doors. If a driver pays attention for them, (usually in the center median) laser using police vehicles stick out like a sore thumb. This knowledge, along with use of Waze has served me well if I find myself inadvertently over the limit.
Yes, don't go any more than 8 miles over the speed limit. Actually works really well too!
Also to remember, most insurance policies do not surcharge you for speeding convictions, up to 9 miles an hour over the limit. ie 64 in a 55mph zone, so
kaichu dento is right.