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 Idaho, being an accessory after the fact is a criminal offense under Idaho Code § 18-205. This statute defines an accessory after the fact as someone who, knowing a felony has been committed, receives, relieves, comforts, or assists the perpetrator, or gives the perpetrator any aid with the intent that they avoid or escape from arrest, trial, conviction, or punishment. The key elements are that the assistance must occur after the commission of the felony, the accessory must have knowledge of the felony, and the intent must be to help the felon evade the legal consequences of their actions. The punishment for an accessory after the fact in Idaho can vary, but it is generally less severe than the punishment for the principal offense. It's important to note that this is distinct from being an accomplice, which involves aiding in the commission of the crime itself. An accessory after the fact may also face charges related to obstruction of justice, depending on the circumstances of the assistance provided to the offender.