Lasar radar is accurate from either direction, coming or going. it only sites in on one vehicle with a straight lasar beam. Crossing the highway, from the air or from behind a bush, makes no difference in the issuance of a citation. Police vehicles go all directions.....all the time. Its necessary for proper law enforcement and is covered by law.

Radar works either way. Doesn't matter. Usually they radio ahead and someone gets you then. They can always give you a ticket! And maybe, it will save your life, or someone elses. I don't mean to be rude, or a smart butt, you just never know when you may need to stop. Do you recall the story of fog on the highway? It came out of nowhere, and sometimes butt heads in front of you can make bad choices. That's all I meant. :)

Radar accuracy is dependent on several factors (beamwidth, bandwidth, PRF, & PRI), most of which cannot be disputed unless you know what they are and can argue them in court more convincingly than the officer. You're best served by getting the make/model of the gun used to clock you and then get the serial number from it. Then file a Freedom of Information Act with the police department to get a copy of the calibration record for the unit. Radar gun manufacturers have a recommended schedule of calibration and servicing they think is needed to keep the unit within advertised operating tolerances. Many PDs do not keep up with this schedule or calibrate the guns using field expedient techniques (e.g. calibrate the gun reading against a patrol car driving at a certain speed at the police station) due to financial constraints. Servicing a radar gun can mean upwards of $500 and a couple of weeks at the gun's service center. If the unit has not been maintained according to the manufacturer's guidelines, you can reasonably argue that the gun's reading of your speed was incorrect. If you try this approach, you need to get the officer to testify that he relied only on the radar gun to gauge your speed and did not use other methods, like timing your progress between two fixed points. If you commit a ticketable offence with the sight of a cop, they can cross whatever barriers they want in order to cite you, so long as it does not put them or other citizens in danger.

I don't understand why so many questions, when taken to basics, seem to say, "I got caught breaking the law. How can I get away with it?" Like all those other similar questions I've seen you don't even say you weren't breaking the law, so I think you should pay up with as much good grace as you can muster.