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In many states the traditional distinctions between the culpability of accomplices and principals to a crime have been replaced by statute—including the felony murder rule that may make an accomplice guilty of first degree or capital murder if he was the lookout or getaway driver for a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 Nebraska, the concept of an accomplice is covered under the state's aiding and abetting laws. According to Nebraska law, a person becomes an accomplice by aiding, abetting, procuring, or causing another to commit any offense. This means that if someone intentionally helps another person in the commission of a crime, they can be charged and prosecuted as if they had committed the crime themselves. This includes acting as a lookout or getaway driver during the commission of a crime such as a bank robbery. Nebraska law does not require the accomplice to be physically present at the scene of the crime to be held liable. Furthermore, under Nebraska's felony murder rule, an accomplice can be charged with first-degree murder if a death occurs during the commission of certain felonies, such as robbery, even if the accomplice's role was limited to assistance rather than directly causing the death. This reflects the state's approach to holding accomplices to the same level of responsibility as the principal offenders.