That might be a state by state law. In WI they have to show you the radar gun if you request it. I've asked to see it, and they complied everytime. I've been let go and been with people who have been let go because the cop hit the trigger twice and the second speed he got was not enough to give a ticket.

Think about it, if they dont need any proof you were speeding, cops could give speeding tickets, to whomever and whenever they wanted. That's why there's laws protecting the citizens.

 

The tint law in Cali is 70% in the front, ANY tint in the rear.

 

So what happens when they pace you or visually determine your speed?

I doubt it's on a state by state basis because of the liability of the matter, but I guess it could happen.