The Felony Murder Rule

If you kill someone while you are committing a felony, you can be charged with felony murder. The rule is applied with strict liability. It doesn't matter if the death is a result of recklessness, negligence, or even a freak accident.

Example
A man commits armed robbery (felony). While driving away from the crime he follows all applicable traffic laws. His brakes go out due to a defective part, and he runs down a pedestrian. He can be charged with felony murder.

Now let's pretend that his brakes were fine, but he was driving recklessly. That would provide the state with two options for charges. They could pursue involuntary manslaughter (criminal recklessness), or felony murder. Murder is the more serious charge. It's also the easier conviction due to strict liability. The state simply has to prove the original felony, and that the defendant caused the pedestrian's death.

People v. Stamp (1969, California)

Facts
Stamp robbed a man, then ran away. A few minutes later the obese victim had a heart attack and died.

Question
Was this murder?

Holding
Yes

Reasoning
Again, strict liability.

Notes
In this case, it would be hard to get any homicide conviction absent the FMR.

Limitations
Many states don't even have a felony murder rule, and some other states have a compromised version. The rule is really aimed at involuntary homicides, since intentional killings will merit murder charges on their own. Often, the rule doesn't hold up well. Remember, we have specific reasons for punishing crime.

You cannot deter someone from being involved in freak accidents. Some rehabilitation, retribution, and incapacitation will be provided as a result of the original felony conviction. And it's a bit strange to reinforce being-careful-when-you-commit-felonies as a societal norm.

Some states use the Misdemeanor Manslaughter Rule instead. It works like felony murder, but with a softer sentence. It basically falls as the least severe of all homicide chargers, beyond even negligent homicide.

Inherently Dangerous Theory
Under this theory, felony murder is invoked only if the felony is inherently dangerous. There are two interpretations of inherent danger.

Some jurisdictions base inherent danger on the category of felony. So things like mail fraud and driving without a license do not provide grounds for felony murder.

Other jurisdictions use a case by case examination. Owning an unregistered handgun is a felony. Cleaning the weapon is not a dangerous activity. If it goes off and kills someone, the FMR is not in play. But waving a pistol around and threatening someone is inherently dangerous. If the pistol goes off and kills the person, you are looking at involuntary manslaughter. If that pistol is unregistered, hello felony murder.

summarized from Life of a Law Student