Prosecutor and Justice of the Peace have no say whatsover with regards to demerit points. Whatever demerit points are assigned to the charge you are convicted of, are the points that you will get.
Prosecutor can offer a plea deal to a different charge though that may have less or no demerits. Remember though that demerits have nothing to do with insurance at all... a 0 demerit charge can still cause your insurance to go up.
+++ This is not legal advice, just my opinion! +++