RickM -- they do require calibration, and the radar was claimed to have been calibrated. I believe training is also required, but I can't find the case law to prove it.
(FWIW, the certification and maintenance records for the radar were for $#!*; mostly illegible, no maint. inside the last 8 years, certification docs messy with conflicting dates, etc.)
Again, the speedo accuracy is no longer in question -- the judge stipulated into fact a peak overtaking speed of 70mph for me.
Dan