An accessory after the fact is a person who (1) assists someone who has committed a crime, (2) after the commission of the crime, (3) with knowledge that the person committed the crime, and (4) with the intent to help the person who committed the crime avoid arrest or punishment. The United States Code defines an accessory after the fact has someone who knows a crime has been committed and receives the offender (harbors them), or relieves, comforts, or assists the offender in order to hinder or prevent the offender’s apprehension, trial, or punishment.

An accessory after the fact is different that an accomplice to a crime, who helps with the commission of the crime. An accessory after the fact is treated as a criminal offense separate from the criminal offense of the offender being assisted, and may be prosecuted as the criminal offense of obstruction of justice.

In Vermont, an accessory after the fact is defined under Vermont Statutes as someone who harbors, conceals, or aids a person who has committed a felony, with the intent to prevent the felon's apprehension or punishment. This is a separate offense from being an accomplice, which involves assisting in the commission of the crime itself. The accessory after the fact must have knowledge that the crime has been committed and must act with the intent to help the offender evade law enforcement or legal consequences. Under federal law, as outlined in the United States Code, an accessory after the fact is similarly someone who assists an offender in avoiding arrest or punishment after a crime has been committed, with knowledge of the crime. The penalties for being an accessory after the fact can vary, but it is generally treated as a serious offense and can result in criminal charges that carry their own set of penalties, distinct from those for the principal offense. In some cases, it may also be prosecuted under the broader category of obstruction of justice.