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 Utah, an accessory after the fact is defined under Utah Code § 76-6-205. This statute outlines that a person becomes an accessory after the fact by knowingly providing assistance to someone who has committed a felony, with the intent to help the offender avoid arrest, trial, or punishment. The assistance can include harboring the offender, providing comfort, or any other form of aid that might impede the offender's capture or prosecution. It is important to distinguish this from being an accomplice, as an accessory after the fact does not participate in the commission of the crime itself but becomes involved after the crime has been committed. Being an accessory after the fact is a separate offense and can be charged as such, potentially leading to criminal penalties including fines and imprisonment. The specific charges and penalties can vary depending on the nature of the underlying felony and other circumstances surrounding the individual's actions.