An accessory after the fact is a legal term for a person who, knowing that a crime has been committed, assists the person who committed that crime in order to hinder or prevent their apprehension, trial, or punishment. This assistance can include actions such as hiding evidence, providing a false alibi, aiding the offender's escape, or concealing the crime from law enforcement. Key aspects of being an accessory after the fact include:

• The person knows a crime has already been committed.
• The person helps the offender after the crime.
• The assistance aims to help the offender avoid arrest, trial, or punishment.

Examples of actions that could make someone an accessory after the fact are hiding a weapon used in a crime, driving a getaway car after a robbery, or providing a false alibi for someone who committed an offense. This offense is distinct from "aiding and abetting," which involves helping the criminal before or during the commission of the crime. Being an accessory after the fact usually carries lesser penalties than the original crime but is still a serious charge. In summary, an accessory after the fact is someone who knowingly helps a criminal after the crime to evade law enforcement or legal consequences. This concept is recognized in legal systems such as U.S. federal law and state laws, where penalties vary depending on the nature of the original offense and the assistance given.