Beware of inadvertently forwarded emails lingering in your clients’ files. If they contain an opponent’s privileged information and you wield them in litigation, it could cost you.

That’s the takeaway from a California Court of Appeal decision upholding a trial court ruling that disqualified Gibson, Dunn & Crutcher from representing McDermott Will & Emery and former McDermott partner Jonathan C. Lurie in a malpractice suit pending in Orange County Superior Court.