According to Tommy Pitaro, the only way to prove it is that he "Has to know the [BadWord] you came out of", which as we all know isn't foolproof either.
I agree with the others above that there is no way in hell Chris Rosenburg could have been made- it was just a wild dream and whoever did that "Documentary" just didn't do enough research.
Physical appearance isn't reliable either. Most people think of an Italian as having black hair, olive skin and brown eyes. I have a nephew with blue eyes and blond hair and he is 100% Sicilian.