The Supreme Court of Nevada has determined, in consolidated cases, that nurses may testify as experts regarding medical causation, only if sufficiently qualified. Williams v. 8th Jud. Dist. Ct.; Sicor, Inc. v. 8th Jud. Dist. Ct., Nos. 56928, 57079 (Nev., decided July 28, 2011). The court also clarified the standard for defense expert testimony on medical causation, ruling that it differs “depending on how the defendant utilizes the expert’s testimony.” Where the defendant “purports to establish an independent causation theory, the testimony must be stated to a reasonable degree of medical probability.” But where the defendant’s alternative causation theory “controverts an element of the plaintiff’s prima facie case where the plaintiff bears the burden of proof, the [expert] testimony need not be stated to a reasonable degree of medical probability, but it must be relevant and supported by competent medical research.”

The issues arose from two separate actions involving a hepatitis C outbreak in a Las Vegas clinic. The plaintiffs alleged that medical personnel injected contaminated needles into purportedly defective anesthetic vials and then reused the vials and injected the plaintiffs with “the now-contaminated” anesthetic. The defendant relied on the opinions of a registered nurse and a professor of medicine, who testified that improper cleaning and disinfection techniques may have caused the plaintiffs to contract hepatitis C, but could not identify a specific piece of equipment that transmitted the virus.

The supreme court disagreed with the plaintiffs that because nurses cannot make medical diagnoses under the law, they are “per se precluded from testifying as to medical causation.” The court agreed, however, that the nurse “did not meet the requirements to testify as an expert regarding medical causation here.” While the nurse had extensive experience with infection control and had written and spoken on the topic, he had “little, if any, experience in diagnosing the cause of hepatitis C.” Accordingly, the court ruled that he could testify as an expert witness “on the subjects of proper cleaning and sterilization procedures for endoscopic equipment” but not as to medical causation.