Their 'case' is already unravelling at the seams.. but I would think if he doesn't turn up.. it is further stuffed.. but equally if he turns up and says "I don't know what was in the vials and I don't know where they went" it is also stuffed.
Remembering that ASADA has to demonstrate to 'comfortable satisfaction' that each player was doped.. a witness who 'doesn't know' is hardly compelling.
"I can't recall"