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In many states the traditional distinctions between the culpability of accomplices and principals to a crime have been replaced by statute—including the felony murder rule that may make an accomplice guilty of first degree or capital murder if he was the lookout or getaway driver for a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 South Dakota, an individual who assists in the commission of a crime is considered an accomplice and can be charged and punished as if they were the principal offender. This includes those who aid, abet, counsel, or encourage the commission of the offense, whether present at the crime scene or not. South Dakota law does not make a significant distinction between the principal and the accomplice in terms of culpability; both can face similar charges and penalties. Additionally, under South Dakota's felony murder rule, an accomplice can be charged with first-degree murder if they were participating in a felony, such as a bank robbery, and a death occurred as a result, even if the accomplice was not the one who directly caused the death. This means that a lookout or getaway driver in a bank robbery that leads to a fatality could potentially face first-degree murder charges, reflecting the state's approach to holding all participants in a felony responsible when a death occurs.