the judge didn't ask because he couldn't. u see, wheter fuentes wants to reveal his clients' identities or nor, he simply can't. the doctor-patient confidentiality rule isn't there to protect the doctor (fuentes), but his patients (all of them, not just those who contacted him to dope themselves). fuentes might give up his own rights, but he certainly can't give up his clients' rights.
let's say the prosecutor ask him to reveal his clients identities and he answers the question. as soon as he would do that, the judge would be compelled to immediately order his answer being struck from the records, as a violation of his clients rights would deem his statement inadmissible in court.
of course u might say "
but those clients are a bunch of cheating bastards!".... but bastards or not, they still have their constitutional rights....besides we can't be sure they all are cheating bastards. and on top of that, even if all those blood samples would belong to cheating bastards and not normal patients, being a "cheating bastard" wasn't a crime when fuentes collected those samples, as doping wasn't a crime (yet).
i know all theese rules often appear like boring quibbles, wich are there only to allow criminals to elude their responsabilities, but that's not the case. procedural law always responds to common sense and those rules are there to prevent abuse of power by a judge or a prosecutor. judges and prosecutors have a huge power in their hands (like the power to prosecute and incarcerate a citizen). those rules are there to avoid prosecution turning into persecution and oppression.
we often underestimate the importance of democratic principles, such as the right of a fair trial. we often see them as nothing but a series bureaucratic cavils, wich are only there to allow some bastards to escape punishment...... but that's only because we never experienced life in a country that doesn't guarrantees such rights.
because any judge, no matter his nationality, would still have to abide by the spanish law. and that's because this event occurred on spanish soil and can only be prosecuted according to the spanish criminal law. that's another of those "key principles" in criminal law. try to imagine what could happen if a north korean prosecutor could apply north korean criminal laws in spain. not only that would go against the very concept of "popular sovereignty"... it would be madness!
even worse, try to imagine what could happen if a private association (even an international one, such as wada) could exercise criminal prosecution over the citizens of a democratic country and force them to give up their constitutional rights... the mere idea is frightening!
i actually believe the judge and the prosecutor did a pretty good job, given what they had to work with. they couldn't prosecute fuentes for doping players (because at that time doping wasn't a crime), so they found an angle and charged him with "endangering public health". that was quite clever!
of course they can't use the same expedient with fuentes patients (as they only "endangered" their own health), but i'm confident they'll come up with something before the appeal is over.