JCali.....they are arguing that the patents Purdue cited in the case have been deemed invalid and therefore under the law they are barred from using the patents as a means to hold up the FDA approval process;
"how many days for the purdue lawyers to respond? does judge need to tell them to respond by a date or is it automatic?"
Found the notes below at http://iposgoode.ca/TheUSPatentLitigationProcess-IPOsgoodeDecember2010.pdf pg 4, 2nd paragraph: If the defendant has asserted counterclaims (e.g., asserting that the plaintiff’s patent is invalid), the plaintiff must serve a reply, which is the plaintiff’s answer to the counterclaims. The plaintiff is required to respond to counterclaims in the same manner as the defendant is required to respond to the plaintiff’s claims—that is, by either denying or admitting the allegations. Replies are due within 21 days after being served with the counterclaims.
Authored in Dec 2010 by:
Irfan A. Lateef is a Partner at Knobbe Martens in Irvine, California. He is a graduate of Georgetown University Law Center (J.D.), Northwestern University (M.S. Biomedical Engineering), and University of Illinois, Urbana-Champaign (B.S.E.E.). Marko R. Zoretic is a Partner at Knobbe Martens in Irvine, California and is the president of the Canadian American Bar Association. He is a graduate of McMaster University (Electrical Engineering and Management) in Hamilton, Ontario and Osgoode Hall Law School (J.D.) in Toronto, Ontario.
Don't know how much(if at all) things have changed since 2010.
Pg 7 of their paper notes "If a patent infringement lawsuit makes it to trial—and less than 5% do—it will likely be a trial by jury. The parties may waive the right to a jury trial and have the court try the case, but such waivers are rare."