IIRC the hand held radars were proven inadmissible in court under appeal a few years ago for the very reasons suggested by you, AFAIK they cant gain a conviction & so rely on our unquestioning compliance, the figures then released by media as unpaid fines (slackers who wont pay their way) were those which were unenforceable.i distinctly remember reading about the appeal taken by a cork businessman who "scored" 12 points & got banned but cant find it now.
Printed copy · Anthology Volume 2, page 1225Printed copy from The Tender For Law Anthology, Volume 2, page 1225 (printed 14 June 2014). Added by this site; not part of the Facebook export.