The thing is: if encryption is illegal and you encrypt your illegal material so law enforcement can't convict you for it, they can still convict you for using encryption.
[1] https://www.google.com.br/search?q=appelbaum+right+to+be+ent...
In other words, introducing "guilty until proven otherwise" introduces witch-trials pretty much by definition: if she floats, she's a witch (so far, so good; yay it works); if she drowns (or dies in notprisonnosirnotatall after years of not confessing nonexistent secrets), she was innocent. Of course, there is absolutely no way this might be abused, and certainly not for personal vengeance.
Welcome to Salem, MA.