Ei incumbit probatio qui dicit, non qui negat (the burden of proof is on the one who declares, not on one who denies).
It is the principle that one is considered innocent unless proven guilty.
Has anyone else seen this (now deleted) comment in the Metallica Fifth member (private) group? It was mentioned that on the Saturday Metallica gig Ozzy will be there to play 2 songs with them. I personaly can't believe this but I would be happy if it is/will be a fact.