When records of an arrest or conviction are sealed or expunged (a notation is made in the file that the records are off limits to all except law enforcement personnel), defendants can, for some purposes, treat the arrests or convictions as though they had never happened. For example, assume that a defendant's conviction for misdemeanor possession of an illegal drug is expunged. On applications for school, a job or a professional license, the defendant may be able to answer that the defendant has no arrests or convictions (assuming no others exist). However, the rules about who is eligible for expungement, and the effect of expungement, vary from state to state, and people interested in expungement should seek the advice of an experienced attorney or the staff of a community-based rehabilitation project that includes expungement as part of its everyday services. These general guidelines apply to many expungement programs:

• People have to apply (in writing) for expungement. Arrest and conviction records are not automatically expunged or sealed after a period of years.

• Even though a conviction has been expunged, in some circumstances it can still be used to increase the severity of a sentence should a defendant again be convicted. For example, an expunged conviction may subject a defendant to a "three strikes" sentencing law.

• Convictions cannot be expunged until about a year after they occur, and then only if the defendant is done serving the sentence and is facing no new charges.

• Not all convictions are eligible for expungement. For example, in many states defendants cannot expunge felony convictions or convictions involving sex offenses. Juvenile and misdemeanor convictions are most often subject to expungement.

• A defendant acquitted of a criminal charge may be able to have the records of the arrest and charge sealed immediately.