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 New York, an accessory after the fact is not recognized as a separate offense under the state's penal code. Instead, New York law addresses similar conduct under different legal concepts such as hindering prosecution or obstructing governmental administration. For example, under New York Penal Law Section 205.50, a person is guilty of hindering prosecution when they render criminal assistance to a person who has committed a felony, with the intent to prevent, hinder, or delay the discovery or apprehension of, or the lodging of a criminal charge against, the person who committed the felony. The degree of the charge can vary based on the circumstances, ranging from a misdemeanor to a felony. Additionally, under Section 195.05, a person is guilty of obstructing governmental administration when they intentionally obstruct, impair, or pervert the administration of law or other governmental function or prevent or attempt to prevent a public servant from performing an official function, by means of intimidation, physical force, or interference, or by means of any independently unlawful act. It's important to note that federal law also addresses accessories after the fact under 18 U.S.C. § 3, which defines the offense and prescribes penalties for anyone who assists an offender in order to hinder or prevent their apprehension, trial, or punishment. The distinction between an accessory after the fact and an accomplice is maintained, with the latter being someone who assists in the commission of the crime itself. In any case involving such charges, it is advisable to consult with an attorney who is knowledgeable in both state and federal criminal law.