Patent law can be awfully complex. Just ask U.S. District Judge Marsha Pechman in Seattle, who had to backtrack from a decision tossing a patent infringement lawsuit against Microsoft Corp. on Friday after both sides suggested she used the wrong standard to dismiss the wrong claim.

The suit was filed in July 2014 by South Korea-based CAP Co. Ltd., which is represented by a team at Hausfeld led by Bruce Wecker. It alleges that Microsoft's Windows applications and various security products widely infringe three CAP Co. patents related to virus and firewall protection. Pechman dismissed the case with prejudice in April after finding no grounds for indirect, direct or willful infringement.

The problem with her ruling was that Microsoft never sought dismissal of the company's direct infringement claims.