This case does not. The district judge did not apply a categorical rule of disqualification but stressed that Joyce and Stensland remained in responsible positions when the 1995 test was devised and used. Of course if, as plaintiffs contend, Joyce and Stensland have no useful evidence to present, then Miner and Arimond should not have been disqualified. But whether they have evidence cannot be determined a priori. It remains to be seen what evidence they have.
Plaintiffs apparently believe that only expert evidence matters to a disparate-impact case.
If that is so, then Joyce or Stensland may have useful evidence, and the confidences might become important. Disputes of this sort illuminate the virtues of the final-decision rule. Instead of trying to predict how the trial will play out, we defer review until the end, when we can see how matters did play out. What a mess it would be if we were to issue a writ of mandamus reinstating Miner and Arimond, and then both Joyce and Stensland give significant testimony. But if, as plaintiffs predict, Joyce and Stensland have nothing to contribute, and Chicago has been crying wolf, then at the end of the case plaintiffs will have a powerful appellate issue.