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 Washington State, the felony murder rule is codified in the Revised Code of Washington (RCW) under RCW 9A.32.030. According to this statute, a person is guilty of murder in the first degree when they commit or attempt to commit a specified felony (such as robbery, burglary, rape, arson, or kidnapping) and in the course of and in furtherance of such crime or in immediate flight from such crime, they or another participant causes the death of a person other than one of the participants. This means that if a death occurs during the commission or attempted commission of these felonies, all participants can be held liable for murder, regardless of who actually caused the death. This includes situations where an accomplice serves as a lookout or getaway driver. The rule applies even if the death was unintentional or if it was a co-felon who was killed, for example, by law enforcement during the commission of the crime. The felony murder rule in Washington thus holds all participants in certain felonies responsible for any resulting deaths, reflecting the state's interest in deterring the commission of inherently dangerous felonies that may lead to loss of life.