In the latest string of adverse rulings against gunmaker Sig Sauer, a federal judge in Massachusetts rejected the firearm manufacturer's attempts to discredit a widely contested expert's opinion that its P320 pistol was defectively designed.

On Monday, U.S. District Judge Denise J. Casper of the District of Massachusetts denied motions by Sig Sauer and Cambridge for summary judgment and attempts to exclude the plaintiff's experts from testifying about the semi-automatic pistol's alleged design defect claims brought by a now-retired police officer, Thomas Ahern.