Was Cardinal Keith O'Brien a serial sexual predator?

Is/was O'Brien a serial sexual predator?
How likely is it that four men colluded to fabricate stories against the Cardinal? Cardinal O'Brien has said that he "contests" the claims against him, but he has refused to deny them outright. A statement on Monday conspicuously lacked a rebuttal. 

One suggestion is as worrying as the accusations. A source within the Catholic Church also said the cardinal "doesn't know who his accusers are and doesn't know what they're accusing him of".  The suggestion that the cardinal doesn't know the charges against him was repeated later. What's happened to Natural justice? In UK law (1) Audi alteram partem (Latin for, hear the other side): no accused, or a person directly affected by a decision, shall be condemned unless given full chance to prepare and submit his or her case and rebuttal to the opposing party's arguments; And high ranking Roman Catholic dignitaries worldwide can understand that because it's also written in Latin. The Vatican is considering what to do and and the man subject to these proceedings apparently doesn't know enough to mount an effective defence. The accused has a right to be heard and needs enough information to prepare an effective defence or rebut charges. We must take O'Brien's word for things that he really doesn't know the charges against him but the cardinal is an experienced member of the Church, his claim that he is denied natural justice is clearly credible and consistent with the way the church does things. Papal powers and powers of superiors generally include ordering accused priests to retire to monasteries. For a man who doesn’t want to become a monk or who can’t adjust to monastic life that amounts to an indefinite prison sentence. It’s unlikely O'Brien will be forced into a monastery but other priests have been ordered in this way. O'Brien has been ordered to "live the life of a hermit" and a "shamed recluse". If the allegations that he was a sexual predator and made at least one victim feel suicidal are true few will feel sorry for him but nothing has been proved in open court and all we know for certain is an admission of unspecified breech of the vow of celibacy.

Why hasn't O'Brien been given details about the charges against him? If he knew more O'Brien could perhaps recognize his accusers, if he's guilty he probably remembers what he did and to which priest. After retiring he can't easily get nasty to his accusers himself but has friends and contacts who could make life very uncomfortable for them. Is there any way of giving O'Brien the information he needs to mount an effective defence and also protecting the accusers? Secular organisations would try and find some way round all this but The Roman Catholic Church apparently thinks it's above ordinary rules like ensuring a fair trial.

The arbitrary power the church can exercise over priests up to the rank of cardinal is at least as ominous as the unspecified allegations made against O'Brien.