The State has two years from the date of arrest to file charges in a misdemeanor matter. If your son has had an arraignment courtdate since his arrest (where you enter a plea of guilty or not guilty) in all likelyhood that has already happened. Once charges are filed, there is no absolute limit to how long the State can take to try a charge in the absence of a filed demand for a statutory speedy trial. At this point, or at some point in the future, your son may be able to bar prosecution by filing a plea in bar alleging a violation of his constitutional right to a speedy trial. The Judge will then consider a number of factors to decide whether to prevent further prosecution or not. Hopefully your son has an attorney to guide him through this technical process.