Legal Question in Criminal Law in California

There are few specific facts which the prosecutor must be prove in order to win a first-degree murder conviction. You're right that the cause of death is a fact that need not be proven. But the prosecutor must prove that the defendant killed the victim, and that she did so with the specific intent to cause death or great bodily injury. These facts are called elements of the crime. The prosecutor had to prove each element, but the law does not say what types of evidence are required in order to prove them. You're right that the jury could have found Ms. Anthony guilty without proof of the cause of death, but that does not make the issue irrelevant. It also does not mean the jury had to ignore the lack of such evidence.

In other words, while the cause of death is not *necessary* information, it is *relevant* information. If the prosecutor had offered such information the jurors could have considered it. They were also allowed to consider its absence.

Jurors must be persuaded, beyond a reasonable doubt, that the defendant committed each element of the crimes charged. These jurors said they had reasonable doubt about whether Ms. Anthony killed her daughter at all, let alone that she had done so with the required intent. The prosecutor's case would have been stronger if he could have shown how the daughter died. After all, he had to provide *some* details even though the law does not say which details they need to be. And while he obviously did provide a lot of information, the jury does not have to agree with him about what information is important and what isn't.

Without knowing the cause of death the jurors had reasonable doubts. Even if they all believed Ms. Anthony was *probably* guilty, their reasonable doubts required them to acquit her.

To clarify part of my prior answer:

In order to win a murder conviction, prosecutors have to prove *who* caused the victim's death but they don't have to prove *how*. Still, evidence of how the victim died is often an important part of proving that someone killed her and that the defendant was that someone.

Imagine that two men, A and B, walk into an empty room together. A while later, A walks out. The next person who walks in finds B's dead body. It turns out that B was shot, stabbed, burned, and bludgeoned. The injuries are all serious and were all inflicted at about the same time, so the medical examiner can't be sure which one caused B's death. Even so, we can be reasonably sure A did it. Jurors could easily convict A under those circumstances without a clear cause of death.

Now imagine that B had also been poisoned. The poison would take effect ten minutes after it is consumed. Five minutes before he and A walked into the room together, B was alone with C -- who hated him and who had some of the same poison in his possession. And imagine that the medical examiner still can't tell which of these events caused B's death. Jurors could have a reasonable doubt about whether A caused B to die, even if they had no reasonable doubt that A had caused all of the physical injuries. There would be a reasonable possibility that C was the one who caused B's death. The lack of evidence of a cause of death would be a perfectly valid reason for jurors to acquit A of murder, even though there is no rule that required the prosecutor to prove the cause of death.