the state/local govt is your accuser, not the cop personally.
Precisely.

Around here it would be.....
Commonwealth of Pennsylvania (or relevant municipality) vs. Poor Slob going too fast.
The most likely situation is that you will be offered a plea, right off the bat (i.e. Lesser speed and lesser fine, but the municipality still gets revenue, and a conviction) Most folks will take the offer and run with it. If you have balls and are lucky, you can bargain for a little more (i.e. a non-point violation) as having points against your license will jack your insurance rates, making the citation cost way more in the long run than what is written upon it. Bear in mind, that if you don't take the offer and are found guilty, you will be paying the full fine and getting all the points that the violation carries.
However, if you feel you have a good chance of beating it and are well prepared, there is no reason not to fight it. The worst case is that you are found guilty of exactly what you were cited for. Nothing more, nothing less.
Using a "set" police officer to represent the municipality is usually used in situations where there is a high volume of citations issued. Without this representative there, there would be less of a chance of the issuing officer being present (i.e. being on-duty at time of hearing, having a day off and not wanting to come to work, etc) It's cheaper for the govt, and
usually gives them the same chance of winning,
in most cases.
However, if you contest the citation, this gives you a better chance of winning because it is also a crap shoot for them. They gamble on the preparedness of the issuing officer. The only testimony or evidence that the "representative" is permitted to offer is what the issuing officer has in their written report. He had better have a well prepared report that covers all his bases. If one has a legitimate defense (for example: questioning the calibration of the device used to clock your speed) and the issuing officer has not provided proof of this (not a great example, as most DO include this certificate) then there really is no chance of rebuttal on the part of the municipality. The "representative" cannot offer verbal testimony as he/she was not there. The burden of proof lies with the prosecution. If they cannot prove, beyond a reasonable doubt, that you are indeed guilty, with the facts that they have, then the Judge will have no choice but to find you not-guilty. He may not like doing it, he may give the issuing officer an earful in private the next time he sees him, but what do you care?
This is very simplified, and I not an attorney by any stretch of the imagination. This is from research, advice from my own counsel and practical application of my rights as a US Citizen.
Perhaps Oldman or some other community member that IS an attorney can lend some credence to this?
(** Edited for punctuation and grammar ** )