'Hybrid Witnesses' and Federal Rule of Civil Procedure 26

Treating physicians provide useful factual testimony about their diagnosis and treatment of plaintiffs alleging an illness or injury. Because of the supposed neutrality of treating physicians, juries may credit their testimony more than that of a so-called independent expert who has been retained by another party to examine and diagnose a plaintiff. But treating physicians are often accessible only to the plaintiff and, accordingly, sometimes more likely to discuss their testimony with plaintiff’s counsel.

Under the old Rule 26, however, treating physicians and many other part-fact/part-expert, or “hybrid” witnesses, had no disclosure requirements. The Civil Rules Advisory Committee for Federal Rule of Civil Procedure 26 recognized this inconsistency when it revised the rule’s reporting and disclosure requirements in 2010.