The problem may be that Sparks is, I hope, a decent and normal person. Thus he may not be persuaded by this argument. I suppose providing him with examples of LA’s previous attempts at intimidation would help, but fairly or not, he may regard the secretiveness as too self-serving.
The big question I have is: did Sparks communicate to USADA exactly how much detail he wants? It seems probably not. So if they give him more details, with no names, are they gambling? Will he get p-d off at them for not giving him more? At this stage of the game, he is very unlikely to give either side one more chance.
There is some subjectivity, yes, but I'm not sure it comes into play in this case. The usual procedure is that if the fluctuations exceed a certain level of probability, the passport is considered suspicious, and goes to an expert panel for further evaluation. Whether it ever gets to the panel is based on objective criteria, whereas the panel's final determination may be based on more subjective factors.
But--barring a coverup of a positive by UCI--none of LA's passport data was judged positive by a panel, so no subjective factors ever came into play. Most likely, though we don't know for sure, none of the data ever even reached a panel.
As others have noted, USADA will probably not be using the passport data as standalone evidence of doping, but only as supporting evidence. They don't have to demonstrate that any fluctuations indicate manipulation with very high probability IF they can show that certain fluctuations closely correlate with witness testimony that LA was blood doping at a particular time. E.g., if shortly after a date a witness claims LA transfused, there were fluctuations in his passport much greater than any in the days or weeks preceding that date, this would be powerful evidence. There isn't much an opposing expert could do except argue that such fluctuations might have happened by chance, illness, whatever. But subjectivity really doesn't play much of a role here. If one has a substantial record of LA's passports, one can determine an approximate probability of such fluctuations.
Anyway, I continue to think this case is almost entirely about witness testimony. The passport data are window dressing, an attempt to show that LA exceeded some scientific parameters. And their use could conceivably backfire on USADA, because it is possible to dope and not affect passport parameters. One thing an opposing expert could do that could really hurt USADA's case is show that other dates when witnesses claim LA manipulated his blood there were no unusual fluctuations at all. Ashenden knows this is easily possible, but try explaining to a panel why sometimes there are fluctuations and sometimes they aren't. If you're going to bring in passport data, you better be certain everything matches up. Otherwise, better to stick to witness testimony exclusively.