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In many states the traditional distinctions between the culpability of accomplices and principals to a crime have been replaced by statute—including the felony murder rule that may make an accomplice guilty of first degree or capital murder if he was the lookout or getaway driver for a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 Michigan, the law does not make a significant distinction between the principal actor of a crime and an accomplice. Under Michigan law, anyone who aids, counsels, or procures the commission of a criminal offense can be charged and punished as if they had directly committed the offense themselves. This is outlined in the Michigan Penal Code, which states that an accomplice may face the same penalties as the principal offender. The concept of 'aiding and abetting' encompasses the actions of an accomplice, meaning that if someone acts as a lookout or getaway driver during the commission of a crime, such as a bank robbery, they can be charged with the same offense as the person who actually perpetrates the robbery. Furthermore, under the felony murder rule in Michigan, if a death occurs during the commission of a felony such as a bank robbery, an accomplice can be charged with first-degree murder, regardless of their role in the crime, even if they were not the individual who directly caused the death.