Without dooming, this is always a possibility in all investigations.

I suspect Hillary has asked the deep state to investigate her on many occasions because once an investigation into a crime is thrown out of court, that's it - it can never be retried.

Also because investigations are often as much about gathering evidence so it can be destroyed rather than submitted as evidence. Once all of the evidence is gathered then oops - there's a mysterious fire or it and all of the server backup tapes are lost.