A federal judge has sided with Allied World Insurance Co. in a legal malpractice insurance dispute involving West Chester-based Lamb McErlane, leaving the law firm uncovered for a $557,001 claim.

U.S. Magistrate Judge Timothy Rice of the Eastern District of Pennsylvania granted Allied World’s motion for judgment on the pleadings on Feb. 23, ruling that the claim originated in May 2015, more than a year before the law firm’s policy period began. Rice said a May 2015 letter outlining allegations against the firm constituted a claim.