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 Mexico, an accessory after the fact is someone who assists a criminal after a crime has been committed, knowing that the person committed the crime, and with the intent to help the criminal evade law enforcement or punishment. This is distinct from being an accomplice, who is someone involved in the commission of the crime itself. New Mexico law, in alignment with federal law, treats being an accessory after the fact as a separate offense. This can include actions such as harboring the offender, providing comfort, or any other assistance that could impede the offender's apprehension, trial, or punishment. The crime of being an accessory after the fact can be prosecuted under the statutes related to obstruction of justice, which is a serious offense and carries its own penalties independent of the principal crime.