Previously, false rumors said that Clinton poured actual bleach on emails or on hard drives associated with the personal servers. According to the Washington Post, the confusionHere’s what Comey had to say on this subject in his July 2016 statement:
It is also likely that there are other work-related e-mails that they did not produce to State and that we did not find elsewhere, and that are now gone because they deleted all e-mails they did not return to State, and the lawyers cleaned their devices in such a way as to preclude complete forensic recovery.
Prosecutors necessarily weigh a number of factors before bringing charges. There are obvious considerations, like the strength of the evidence, especially regarding intent. Responsible decisions also consider the context of a person’s actions, and how similar situations have been handled in the past.