Leavitt v. Siems, — P.3d — (Nev. 2014)
In this case, the Nevada Supreme Court reaffirmed its previous holding in Williams v. Eighth Judicial District Court, 262 P.3d 360 (Nev. 2011), which provides that a defense expert’s testimony regarding alternative causation need not be stated to a reasonable degree of medical probability when it is being used to controvert an element of the plaintiff’s claim, rather than to establish an independent theory of causation.
As both Leavitt and Williams explain, the application of the reasonable-degree-of-medical-probability standard hinges on the purpose of the testimony:
“Any expert testimony introduced for the purpose of establishing causation must be stated to a reasonable degree of medical probability. However, defense experts may offer opinions concerning causation that either contradict the plaintiffs expert or furnish reasonable alternative causes to that offered by the plaintiff, without having to meet that standard.
This distinction exists because when defense expert testimony regarding cause is offered as an alternative to the plaintiffs theory, it will assist the trier of fact if it is relevant and supported by competent medical research. Accordingly, once a plaintiffs causation burden is met, the defense expert’s testimony may be used for either cross-examination or contradiction purposes without having to meet the reasonable-degree-of-medical-probability standard, so long as the testimony consists of competent theories that are supported by relevant evidence or research. This lowered standard is necessarily predicated on whether the defense expert includes the plaintiff’s causation theory in his or her analysis.”