Here's the deal.
1. They do not have to show you the radar.

2. Do not go in there and say your Speedo cable was broke, hence the 81 in a 55mph zone. The judge will laugh you out and then hammer you. I have personally seen a judge hammer someone and say....You can't tell the difference between 50 and 80. Thirty miles over the speed limit.......
81 in a 50 will usually get you a couple days in jail at the beach.

3. You're friend and you with the same attorney could work out if your friend is willing to go into court and say he was speeding, passed you but you were just driving normally. If he admits to what he did(getting you in trouble with him) he may gain some credibility with the judge. That will help you.
If he goes in there and denies speeding when he was, you'll get no sympathy from the judge and you'll probably go to jail.

So it comes down to how good of a friend is he. Is he willing to tell the truth or would he prefer to buy you a tube of KY since he and the judge will have their way with you!