At the trial of a personal injury case, it is critical for the plaintiff to establish not only the nature and extent of her injuries, but also that those injuries were caused by the defendant’s negligence. Ordinarily this medical “causation” evidence is presented through expert opinion testimony of the physicians and other health care providers who treated the plaintiff following the incident.
Expert Witnesses at Personal Injury Trials
Most witnesses who testify at trial are permitted to state only facts and not opinions. However, the law of evidence permits witnesses with “specialized knowledge” which will assist the jury in deciding a fact at issue in the case to give expert opinion testimony. Because most individuals serving on juries do not have a medical background, medical doctors are understood to possess specialized knowledge necessary to assist the jury by providing opinions as to the plaintiff’s diagnosis and the cause of her injuries.
But what about other health care providers who may have opinions on the plaintiff’s injury, but who are not licensed medical doctors? Are they permitted under the law of evidence to state causation opinions at trial? The answer to this question can be complicated, and hinges on rules established by court decisions as well as statutes passed by the legislature.
Rules Governing Expert Witnesses
The Supreme Court has established the general rule that only medical doctors are permitted to give expert testimony about the cause of a physical injury. In John v. Im,  the Court held that a licensed psychologist was not permitted to testify that the plaintiff sustained a mild traumatic brain injury in an automobile collision, because he was not a medical doctor. Similarly, in Hollingsworth v. Norfolk S. Ry., the Court held that two licensed podiatrists were permitted to testify to the treatment they rendered to the plaintiff, but not to their opinions of the cause of the plaintiff’s injury, because by statute the practice of podiatry did not include rendering diagnoses.  One notable exception to this rule is the case of Velazquez v. Commonwealth,  in which the Court permitted expert testimony by a “sexual assault nurse examiner” as to the cause of the victim’s physical injuries in a case of sexual assault.
The Supreme Court has issued a separate line of opinions concerning expert testimony on mental disorders. In Fitzgerald v. Commonwealth,  the Court permitted a licensed professional counselor to testify that the victim in the case suffered from post-traumatic stress disorder (“PTSD”), noting that the statutes regulating professional counselors specifically authorized counselors to make such diagnoses. The Court reached the same conclusion in Conley v. Commonwealth,  in the context of a licensed clinical social worker’s diagnosis of PTSD. It is interesting to note that even though these rulings permitted the witnesses to testify to the diagnosis of PTSD, the Conley Court specifically mentioned that “the proffered expert was not offered to testify regarding the cause of the victim’s diagnosed mental disorder,” perhaps signaling a different outcome had direct causation testimony been proffered. 
Types of Opinions Allowed by Expert Witnesses
In addition to these and other decisions by the Supreme Court, the Virginia General Assembly has passed a number of statutes which create rules for the types of opinions specific health care providers are permitted to state at trial. For example, chiropractors, when properly qualified by the court, are expressly permitted to testify as an expert witness as to the “etiology, diagnosis, prognosis, treatment, treatment plan, and disability,” so long as that testimony remains within the scope of practice of chiropractic as it is defined in Section 54.1-2900 of the Virginia Code. 
More recently, expert testimony by physician assistants and nurse practitioners has come within the scope of this statute. In 2014, the General Assembly passed a law permitting properly qualified physician assistants to testify as an expert witness as to “etiology, diagnosis, prognosis, treatment, treatment plan, and disability.”  The rule was expanded to apply to nurse practitioners in 2015. These amendments reflect the realities of the contemporary practice of medicine, in which a patient may receive care from a physician assistant or nurse practitioner, but never actually see a medical doctor. Interestingly, however, the statute expressly prohibits physician assistants and nurse practitioners from testifying as an expert witness against a medical doctor in a malpractice action, on the issues of standard of care and causation. 
Because the success of a plaintiff’s personal injury case can rise or fall on proving that her injuries were caused by the defendant’s negligence and not some other source, it is critical for the plaintiff’s attorney to be familiar with the rules of evidence governing expert medical testimony.
About the Author: David M. Irvine is an experienced trial attorney focusing his practice on personal injury law working in the firm’s Charlottesville, Virginia office. He has handled cases involving car accidents, catastrophic injuries and wrongful death and has litigated cases across the Commonwealth on behalf of deserving clients. David has published on topics related to litigation in wrongful death cases and trial procedure and regularly speaks on litigation topics.
 279 Va. 360 (2010). After the Hollingsworth case was decided, however, the General Assembly amended the statutory definition of podiatry to include not only the treatment, but the “diagnosis” of foot conditions. See Va. Code 54.1-2900.