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In many states the traditional distinctions between the culpability of accomplices and principals to a crime have been replaced by statute—including the felony murder rule that may make an accomplice guilty of first degree or capital murder if he was the lookout or getaway driver for a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 Utah, an individual who assists in the commission of a crime is considered an accomplice and can be charged and punished as if they had committed the crime themselves. This includes those who aid, abet, or encourage the principal offender, as well as those who are present at the crime scene and participate in some way, such as acting as a lookout or getaway driver. Utah law does not strictly differentiate between principals and accomplices in terms of liability; both can face the same legal consequences. Furthermore, under Utah's felony murder rule, an accomplice to a felony that results in death can be charged with murder, even if they did not directly cause the death. For instance, if a bank robbery orchestrated by multiple individuals leads to a fatality, all participants, including the lookout or getaway driver, could potentially be charged with first-degree murder.