The felony murder rule is a legal doctrine that expands the definition of murder and makes criminal accomplices (including a lookout or getaway driver) as responsible for a death that occurs in the course of a dangerous felony crime as the person who directly caused the death by pulling the trigger of a gun, stabbing the victim with a knife, strangling the victim, or otherwise causing the victim’s death. Examples of dangerous felony crimes that implicate the felony murder rule include robbery, burglary, rape, aggravated kidnapping, carjacking, and arson.

When the felony murder rule applies, it may make a criminal accomplice liable for murder even if the criminals had agreed that no one would be killed in the course of the crime, and even if it is a fellow criminal who is killed in the course of the crime—such as when a police officer or security guard shoots a bank robber—which may result in all other accomplices to the crime being charged with murder.

In many states the felony murder rule—and any distinctions between the culpability of accomplices and principals to a crime—are located in the state’s statutes—often in the penal or criminal code.

In Illinois, the felony murder rule is codified in the Illinois Compiled Statutes under 720 ILCS 5/9-1(a)(3). This statute expands the definition of murder to include deaths that occur during the commission or attempted commission of a forcible felony, such as robbery, burglary, arson, kidnapping, aggravated criminal sexual assault, and other felonies inherently involving a risk of physical harm to others. Under this rule, if an individual commits or attempts to commit a forcible felony and someone dies as a result, all participants in the felony can be charged with first-degree murder, regardless of their intent or whether they were the direct cause of the death. This includes accomplices such as lookouts or getaway drivers. The rule applies even if the death is accidental or if it is a co-felon who is killed, for example, by law enforcement during the commission of the crime. It's important to note that the application of the felony murder rule can be complex and may involve considerations of specific case law and judicial interpretations.