Clarification/Follow-up by voiceguy2000 on 09/30/03 12:30 pm:
I had no inkling that this hypothetical was based on Moses killing the Egyptian slave master who was whipping a Hebrew slave.

In some systems, slaves were considered chattels (personal property) rather than persons, such that killing a slave would carry no more grave consequences than would killing a mule.

However, I have little doubt that under the Pharaoh, Egyptian slave masters were considered persons.

The crucial difference between manslaughter and murder (and indeed the various degrees of murder) has to do with the intent (mental state) of the accused.

Imagine that A sails a paper airplane in the direction of B. Through some utterly bizarre and unforeseeable quirk, the paper airplane happens to hit B in just such a way as to kill him instantly. What result?

We would not call this murder. A had no intent to kill. His only intent was to sail the paper airplane, which is not normally a dangerous activity. Indeed, because it is not a dangerous activity, we probably cannot even say that there was an actus reus (wrongful act). At best, this would be termed manslaughter (if it was charged at all), and probably involuntary manslaughter in a jurisdiction that recognizes the distinction.

Consider, on the other hand, someone who fires a gun through a closed door, not knowing if there is anyone on the other side. If a victim is killed, the shooter will probably be liable at least for second degree murder, because while he had no actual intent to kill, firing the gun that way meant he was recklessly indifferent to the possibility that someone would be killed. The gun is a deadly weapon (unlike the paper airplane), and the intentional firing of it under these circumstances would constitute a mental state sufficient to support at least second degree murder.

Last scenario: A, intending to kill B, fires a gun at B. B ducks, and the bullet hits and kills C, an innocent bystander. What result?

Answer: In most jurisdictions, A is guilty of first degree murder, even though she did not kill her intended victim. Her intent to kill B is "transferred" to the killing of C. It is enough that she intended to kill somebody, and succeeded.