In California, when you talk about “criminally negligent homicide” you’re talking about a crime called “involuntary manslaughter.” It’s the crime that Michael Jackson’s doctor was charged with, for administering a fatal dose of propofol. The crime requires that the defendant do a crime, or a lawful act in an unlawful manner, that caused someone’s death, with criminal negligence.
So what is criminal negligence in California? The instructions that a judge reads to jurors say, in part:
Criminal negligence involves more than ordinary carelessness, inattention, or mistake in judgment. A person acts with criminal negligence when:
1. He or she acts in a reckless way that creates a high risk of death or great bodily injury;
AND
2. A reasonable person would have known that acting in that way would create such a risk.
In other words, a person acts with criminal negligence when the way he or she acts is so different from the way an ordinarily careful person would act in the same situation that his or her act amounts to disregard for human life or indifference to the consequences of that act.
I have added some hopefully helpful bold type here. But hopefully the distinction is clear. On one hand, you have ordinary carelessness or an accident. This is not criminal. On the other hand, you have recklessness that is so different from usual care that the person is essentially indifferent to human life. That’s what rises to the level of criminal negligence. Put another way: criminal negligence is not just any negligence that results in death. It’s a reasonably high standard, as befits a criminal statute that carries prison time as a consequence for its violation.
Merely picking up a gun and having it accidentally go off is unlikely to be found to be criminally negligent. Waving it around or brandishing it is closer to the type of behavior that this crime targets.