One challenge of trial work is trying to anticipate beforehand every issue that might arise once the parties are in the courtroom. Discovery greatly reduces the incidence of surprises of fact, but it can’t protect against surprises of law — foreseeable legal arguments that lurk undetected, camouflaged by the obvious issues absorbing everyone’s attention, until they come leaping from hiding in the course of trial. The Eighth Circuit recently decided a question of preclusion that appears to have ambushed the judge and the attorneys who tried the case in this way. Two sets of plaintiffs represented by the same law firm brought factually almost-identical but legally distinct claims against the same defendant. The claims were tried together, with the judge to decide one set of claims and the jury to decide the other. When the jury reached its verdict first, a camouflaged legal issue reared its head, and the parties found themselves embroiled in a dispute whether the jury’s verdict should bind the judge based on the doctrine of collateral estoppel (issue preclusion), or whether the judge was free to reach a verdict inconsistent with the jury’s decision.