Kelly hit the nail on the head.
That being said, I would like to point out something so as to avoid distraction from the real issue. The OJ Simpson/George Zimmerman example is faulty.
OJ Simpson and George Zimmerman were questions of fact, properly reserved for a jury of their peers.
I don't know specific California and Florida statutes so I am going to use the common law definitions.
Murder is a voluntary killing of another human being the malicious aforethought (in other words, premeditated and malicious murder).
Guilty Act - Murder
Guilty Mind - Intent to kill (even if Zimmerman acted in self-defense, he still had to intent to kill in defense)
There is an act, there is intent underlying the act, as such, it is a crime.
Therefore, the question turns to the jury to determine whether or not the state has properly proven each element of the crime beyond a reasonable doubt. The elements are:
Voluntary killing of another human being
With malicious aforethought (premeditation)
The jury must consider whether the state proved these two elements, beyond a reasonable doubt. These are questions of FACT for the jury to determine, unless the prosecution fails to make even a prima facie case (a case that a reasonable jury MIGHT find for the prosecution, its not a high standard), in which case a judge may dismiss it as a matter of law.
Now with Zimmerman, it is a bit more complicated as he adopted an affirmative defense (a defense where you acknowledge that you committed the crime but offer a legal justification, in his case self-defense), therefore the burden shifted to him to prove that he did act in self-defense and once he made a prima facie case of that, the burden shifts to the state to prove beyond a reasonable doubt that he did not.
But I digress, had the state been unable to establish a baseline guilty act supported by guilty intent, Zimmerman nor OJ could have even been indicted. Murder is a bad example because it is a per se case (intent is apparent on the face, due to the fact that someone is dead, through stabbing, whoever killed them had an intent) so let's use actus reus. Say the state could not find a body or any real evidence that anyone was ever killed. They have failed to show a guilty act. As such, legally, no crime took place (to clarify, you do not always need a body to establish an act of murder, but that is way off the point).
With Zimmerman and OJ we know that a crime took place, so it is a FACTUAL question of whether or not the Defendants committed the crime.
Now let's shift to the Clinton case using The Espionage Act for an example.
The guilty act would be transmitting the documents
The guilty intent would be doing so with the intention to provide the documents to a foreign government or actor.
There is a guilty act --- transmitting the documents to an unsecured government server.
There is no guilty mind though. There is absolutely NO evidence, even prima facie (which is again, low standard) to indicate that Clinton had any intention to transmit the documents to a foreign actor so that eliminates all but subsection F of the Espionage Act.
For a recklessness standard to apply (that is to say she was guilty of intending to behave recklessly), as is prescribed by Subsection F of the Espionage Act one of three requirements would have to be met:
Either she must have acted with GROSS NEGLIGENCE (a term of art...think along the lines of doing a line of coke with a member of the KGB and giving that person state secrets...that would be grossly negligent, not simply using an email server, that is what the law would define as mere negligence);
OR
She had to have knowledge that she was illegally removing the documents (and the laws with emails were at best unclear...you cannot charge a citizen with crime if the law does not specifically prohibit the crime or is unsettled);
OR
She had to have knowledge that a foreign actor had obtained these documents and then not reported it to a superior, which simply does not fit the factual scenario present.
In any of those three situations, she could have been charged under subsection F simply for reckless behavior (as the intent would be the intent to act recklessly). She did not.
Therefore there is not a LEGALLY sufficient case that she violated a law. As such, a prosecutor is FORBIDDEN from bringing charges. It would be against the Rules of Professional Responsibility and it would subject the prosecutor to a tort action of malicious prosecution (and probably some criminal liability as well)
There is a guilty act (transmitting documents), there is no guilty mind (as prescribed by the intent requirement of the statute).
Ergo, no charges can be filed for there is nothing to charge.
Meanwhile, with OJ/Zimmerman a crime undoubtedly took place (there was a guilty act with a guilty mind) so it was a FACTUAL question. In OJ's case whether or not he committed the crime, in Zimmerna's whether or not there was justification for the crime.
With Clinton, at this point, it was a legal question about whether an underlying crime even took place. It did not, not as is statutorily defined.