Quidel shares traded down 21% on Friday afternoon after a judge from the Superior Court of San Diego ruled in summary judgement that a provision in the Beckman/Quidel deal restricting Beckman's ability to commercialize an alternative BNP or NT-Pro BNP assay was void, Piper Jaffray analyst William Quirk tells investors in a research note. The obvious implication here, if the appeal fails, is that Beckman can develop its own test and, over time, push Quidel aside, Quirk adds. The analyst continues to believe the existing deal will be upheld, but he expects Quidel shares are likely to trade sideways ahead of the appeal to the 4th Circuit. He keeps an Overweight rating on the shares with a $73 price target.