just stumbed across this and thought i should post a comment/question if he is still reading this
you can't be arrested for "having backups", you can be arrested for copyright infringment. with that said, how can the cops charge you with copyright infrigment without knowing if you have originals or not. from what you said, they just found them and took them, and unless they were labled "pirated" or you told them that, how could they even say it was illegal
and i'm not sure about this, but unless its federal or governed by a bigger agency, can't only copyright holders press charges for copyright infringment?
just my 2 cents,
good luck