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In many states the traditional distinctions between the culpability of accomplices and principals to a crime have been replaced by statute—including the felony murder rule that may make an accomplice guilty of first degree or capital murder if he was the lookout or getaway driver for a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 New Mexico, an individual who assists in the commission of a crime can be charged as an accomplice. New Mexico law does not strictly differentiate between principals and accomplices; both can be held liable for the crime itself. This means that someone who acts as a lookout or getaway driver during the commission of a crime, such as a bank robbery, can face the same charges as the person who directly commits the criminal act. Furthermore, under New Mexico's felony murder rule, if a death occurs during the commission of a felony, such as a bank robbery, an accomplice can be charged with first-degree murder, even if they did not directly cause the death. This is because their participation in the felony contributed to the circumstances that led to the fatality. An attorney can provide more specific guidance on how these laws may apply to individual circumstances.