If you've been arrested and are on bail, odds are you have already been charged. There are a few states that might allow for a charge to be stayed pending further investigation; but laws vary by state.

The police don't have to prove that you're lying. They simply need to convince a prosecutor that there is probable cause that a crime was committed -- something you appear to be conceding -- and that you were the person who committed the crime.

You should speak to a criminal defense lawyer. If you have not already done so, talk to your lawyer about the information you can provide to the police about your friend and his actions, and how you might preserve evidence that will show that it was not you who committed the crime.