I was charged with a misdemeanor a and b. I'm not guilty of this crime. When I went back to court they offered me a violation with three days community service. My lawyer said it's because they have no case that's why they dropped it from a crime to a violation. Without knowing the case do you think this is the reason they dropped it? Or could there be other reasons?

It is common to "plea bargain" in criminal court. An arresting officer will charge someone with an offense; it is his call to make. When the case gets to a magistrate or prosecutor, the charge may be reduced to avoid the time and expense of trial. You are on the hotseat, and must decide whether to agree to the deal or go to trial.

So a plea is common. Then it does not mean they have no case.

Unfortunately, the criminal court system is sort of like a poker game. Your attorney should be able to evaluate the merits of the case and see a bluff for what it is. I would never advise a client to plea bargain a case in which he is innocent; having said that, I pled nolo to a speeding case to avoid the judge believing the arresting officer and making me pay double the fine for going to trial. It's a tough world.