For immigration purposes, a conviction requires either a formal adjudication of guilty or a withheld adjudication of guilty coupled with a restraint on the person's liberty.  The Third Circuit has determined that a Pennsylvania "determination of guilt without further penalty" qualifies as a conviction because it entails a formal finding of guilt, even though it does not include any restraint on a person's liberty.  The court rejected the argument that because the federal definition of a formal judgment of guilt includes "a plea, finding, adjudication, and sentence," a state criminal scheme that permits a guilty finding without the imposition of a punishment can not qualify as a conviction for immigration purposes. 

The full text of Frias-Camilo v. Attorney General can be found here: