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In many states the traditional distinctions between the culpability of accomplices and principals to a crime have been replaced by statute—including the felony murder rule that may make an accomplice guilty of first degree or capital murder if he was the lookout or getaway driver for a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 Tennessee, an accomplice to a crime is defined under the state's criminal law as someone who assists, encourages, or facilitates another person in the commission of a crime. Tennessee law does not make a significant distinction between the principal offender and the accomplice; both can be charged and punished to the same extent as if they had personally committed the offense. This is in line with the state's aiding and abetting statutes. Furthermore, under Tennessee's application of the felony murder rule, an accomplice can be charged with first-degree murder if a death occurs during the commission of a felony, such as a bank robbery, even if the accomplice's role was limited to being a lookout or getaway driver. The law recognizes that by aiding in the felony, the accomplice has contributed to the circumstances that led to the death, and therefore shares in the criminal liability for the homicide.