My son was charged with dui Florida 316.193(1) in 2009. In court, the people could not proceed and the case was closed. (case not prosecuted) On 10/18/2011, two years later,he was served with a summons to appear for this charge at this time bearing a new docket number. Can he be charged now for a case that is listed as closed since he paid a fine in 2009 for careless driving on this same incident. All violations are listed as closed.

It is one year.
Florida Criminal Statute of Limitations Laws - FindLaw (http://law.findlaw.com/state-laws/criminal-statute-of-limitations/florida/)

Here (http://www.flsenate.gov/Laws/Statutes/2011/775.15) is the text of the statute.