I have always thought that when an umpire in cricket has to decide whether to give someone out LBW or not, they have the hardest decision of any sporting official. The reason for this is that the decision their having to make is not “what has happened?” but “what would have happened?”.
In the same way when a Judge is deciding how to award damages in a professional negligence case, he has to decide what would have happened if the Solicitor or other professional had not been negligent. Inevitably, this is not a precise science and the Judge can only use his best estimations as to what would have happened in certain set of circumstances. Further, the more variables there are the more complicated it gets for the Judge. This is why often when I am asked by my clients, “how much is my professional negligence claim worth”, there is often such a wide spectrum of possible outcomes because of those decisions a Judge has to make.
These days of course, cricket umpires have the benefit of technology to assist in making their decisions. For better or worse in law we are simply have to rely on Judges to make the decisions.