Vixen
Penultimate Amazing
For now let's take as givens that he killed Meredith by himself and that he had barely visible scars on his hands.
He had decided that his story would be that a stranger came in while he was on the toilet and killed her, but that he had confronted the knife wielding blond Italian. As proof of this he showed the Germans the marks.
An alternative is that he had managed to murder her without cutting himself but wanted the evidence of his heroic battle and cut his own hand lightly shortly after arriving in Germany.
I don't believe that the ILE would figure out that Rudi's blood they found early on would spoil their case against Amanda.
That was not deemed by the courts, the pathologist, the luminol and DNA experts, so, no, not "given".