LASER speed gun potentially unreliable and inaccurate

A UK television show casts serious doubt over the reliability of speed measurements taken using the widely-used LTI 20-20 LIDAR (LASER) speed gun. A leading expert in the field of LASER distance and speed measurement throws a spanner into the Government spin machine that tells us these devices are infallible. I wonder how many prosecutions have been brought about and subsequent lives ruined through loss of jobs etc based on readings that were simply not correct...?