It is prudent strategy to have a testifying medical expert who is board-certified in the same medical specialty as the defendant physician. This ensures that the expert has the proper training to testify regarding the standards of care of the defendant practitioner with similar medical training. In this way, the expert cannot be impugned for being underqualified.
There are exceptions, however. If the expert has a lower level of training than that held by the defendant physician, he/she may still be able to opine provided that 1) he/she completed the same lower level of specialty training and 2) the standard of care in question is ordinarily associated with that lower level of training.
In Ivory v. Hackensack University Medical Center, Appellate Division, the plaintiff's medical malpractice complaint had been dismissed by a lower court because plaintiff expert was an internist who failed to establish that he had a background or qualifications in Gastroenterology or that he had recently practiced Gastroenterology, which is a sub-specialty of Internal Medicine. The defendant physician limited his practice to Gastroenterology, although he had also been trained as an internist and was board-certified in Internal Medicine.
However, the dismissal was reversed and remanded by the Appellate Court because the defendant physician, who had failed to adequately diagnose bacterial endocarditis, breached a standard of care that would have been owed by an Internist, not a Gastroenterologist. The Appellate Court found that the Trial Court erred in determining that the alleged malpractice involved Gastroenterology, rather than the shared specialty of Internal Medicine. Accordingly, the expert was qualified to provide an Affidavit of Merit, which limited its reach to defendant's duty of care as an Internist in reviewing the patient's history -- before performing the actual procedure.