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 Massachusetts, the felony murder rule is a legal doctrine that holds all participants in certain felonies liable for any deaths that occur during the commission of the felony, regardless of who actually caused the death. This means that accomplices, such as lookouts or getaway drivers, can be charged with murder if someone dies during the commission of a felony like robbery, burglary, rape, kidnapping, carjacking, or arson, even if the death was unintentional or caused by a third party, such as a police officer. The rule is intended to deter individuals from participating in felonies that could foreseeably result in death. The felony murder rule in Massachusetts is not a separate statute but is incorporated into the state's common law, which is law derived from judicial decisions rather than statutes. It is important to note that the application of the felony murder rule can be complex and may vary depending on the specific circumstances of each case.