-snip-
Think of this simple analogy. Presumably Lauda and aTriz were friends before this incidence, would you expect a friend to participate in the firing squad once a sentence is laid down? I certainly wouldn't.
I would gladly testify and if ordered to punish, would do so; I don't continue friendships with liars and cheats. What's the guarantee that the liar won't fuck my cat behind my back? He/She has lost my trust, I'd ask the individual to Fuck Off.