A federal magistrate has ruled that a medical malpractice insurance carrier may not use the report of its expert in a lawsuit against a rival carrier and broker since it did not provide the defendants with research, largely relied on by the expert, during discovery.

In two intertwined but unconsolidated cases, U.S. Magistrate Tonianne Bongiovanni, sitting in Trenton, said allowing the plaintiff carrier, New Jersey Physicians United Reciprocal Exchange, to use the expert’s testimony against the two defendants—The Medical Protective Co. and Boynton & Boynton Inc.—would be unfair.