Because the law that Comey could have charged her for gross negligence under, is a law from the Espionage Act.
Just because USC 18 -793 appears under the Espionage Act -- it has nothing to do with Espionage.
(f)
Whoever, being entrusted with or having lawful possession or control of any document, writing, code book, signal book, sketch, photograph, photographic negative, blueprint, plan, map, model, instrument, appliance, note, or information, relating to the national defense, (1)
through gross negligence permits the same to be removed from its proper place of custody or delivered to anyone in violation of his trust, or to be lost, stolen, abstracted, or destroyed, or (2)
having knowledge that the same has been illegally removed from its proper place of custody or delivered to anyone in violation of its trust, or lost, or stolen, abstracted, or destroyed,
and fails to make prompt report of such loss, theft, abstraction, or destruction to his superior officer—
Shall be fined under this title or imprisoned not more than ten years, or both.
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It's no difference than the standards for tampering with a chain of evidence in the criminal justice world. If you remove that evidence from it's proper "chain of custody" by gross negligence of your duty to KEEP it within the prescribed channels and documentation. .
She REMOVED herself from "the proper place of custody" by CREATING several networks for REMOVING classified information from the APPROVED channels it needs to flow in..
That's INTENT and that's "gross negligience"..