A criminal accomplice is a person who knowingly, voluntarily, or intentionally assists another person in the commission of a crime—or under some circumstances, a person who fails to prevent another person from committing a crime. Unlike a person who aids and abets a crime by helping with the planning of the crime but is often not present at the scene of the crime—and unlike an accessory after the fact, who is not present at the scene of the crime but assists after the commission of the crime to help the perpetrator avoid arrest or punishment—an accomplice actively participates in the commission of the crime. For example, a person who acts as a lookout or getaway driver for a bank robbery is an accomplice.

In many states the traditional distinctions between the culpability of accomplices and principals to a crime have been replaced by statute—including the felony murder rule that may make an accomplice guilty of first degree or capital murder if he was the lookout or getaway driver for a bank robbery that resulted in a death.

In Oregon, the law does not distinguish sharply between principals and accomplices in the commission of a crime. Under Oregon Revised Statutes (ORS) 161.155, a person is considered an accomplice to a crime if they, with the intent to promote or facilitate the commission of the crime, aid or abet the principal offender. This means that an accomplice can be charged and prosecuted as if they had committed the crime themselves. This includes being present at the crime scene as a lookout or acting as a getaway driver. Furthermore, under the felony murder rule in ORS 163.115, if a person is an accomplice in a felony that results in death, such as a bank robbery, they can be charged with felony murder, which is a form of first-degree murder, even if they did not directly cause the death. This reflects the state's policy of holding all participants in certain felonies accountable when a death occurs, regardless of their specific role.