The balance between “possible” causes and rampant speculation

On May 26, a California Court of Appeal held - for the first time in California - that a party who does not have the burden of proof on an issue may present expert opinion "expressed to less than a reasonable medical probability." Kline v. Zimmer, Inc. (2002) 79 Cal. App. 5th 123, 127. In Kline, the plaintiff had sued the manufacturer of a hip implant Zimmer, Inc. after the plaintiff experienced severe pain following his hip replacement surgery. Id. The plaintiff's experts had opined to a "reasonable medical probability" that the defective hip implant failed and eviscerated plaintiff's opportunity for a "good high percentage treatment available" to relieve him of his chronic hip pain. Id. By contrast, the trial court had excluded the opinions of the hip implant manufacturer's expert as to "possible" alternative causes of the plaintiff's pain because those opinions were "expressed to less than a reasonable medical probability." Id. The Court of Appeal reversed the judgment on the basis that the trial court's evidentiary ruling was error. The Court of Appeal held that the hip implant manufacturer, which did not have the burden of proof on medical causation, was entitled to show that the plaintiff had not met his or her burden of proof by "offering expert opinions offered to less than a reasonable medical probability." Id. at 509.

At first blush, the holding may appear to open the floodgates of "possible" medical causes of a plaintiff's injuries. For example, imagine a claim alleging a fairly common fact pattern that a fitness gym or other facility did not respond fast enough to save the life of a man suffering a heart attack. One could imagine defense's cardiologist expert attempt to list every possible cause of a heart attack that prejudices the jury against the plaintiff, including drugs, alcohol, smoking, high cholesterol, high blood pressure, obesity, and on and on. Where medical causation is disputed, could a defense expert begin to list every possible cause of a plaintiff's injury under the Kline holding? The answer is no.

Recognizing potential abuse of the kind described, the Kline Court of Appeal expressed clear limits to its holding. An expert may not base his or her opinion "on assumptions of fact without evidentiary support ... or on speculative or conjectural factors." Id. at 134. The Court of Appeal used an example to show the difference between possible alternative causes grounded in case-specific facts and pure speculation. In a footnote, the Kline Court of Appeal explained that the expert in Kline could not opine that a "Vitamin D deficiency could cause pain of the nature [the plaintiff] was experiencing" because there was no evidence in the record the plaintiff had such a deficiency. Id. at 134 n. 7. Such an opinion by the defense expert would be conjecture and speculation. By contrast, the Kline Court of Appeal explained that the expert could opine that a possible alternative cause of the plaintiff's pain was attributable to other conditions plaintiff actually had. The difference between improper speculation and an opinion of a possible alternative cause is "necessarily shy of the 50 percent likelihood cutoff imposed on Zimmer in this case," but greater than impossible. Id. at 134.

While the Kline Court of Appeal sided with federal case law on this issue, other States have decided that every expert opinion on causation must be stated in more certain terms than a mere possibility. See Iowa Power & Light Co. v. Stortenbecker, (Iowa Ct. App. 1983) 334 N.W.2d 326, 331); Morsicato v. Sav-On Drug Stores, Inc. (Nev. 2005) 111 P.3d 1112, 1116; Hunter v. Ura (Tenn. 2005) 163 S.2.3d 686, 704. These States usually require the expert to state opinions to a reasonable degree of medical certainty or some variation of such a phrase regarding the expert's certainty. See, e.g., Morsicato, 111 P.3d at 1116 ("[M]edical expert testimony regarding ... causation must be stated to a reasonable degree of medical probability").

Kline's bar on speculative or conjectural expert opinions regarding "possible" alternative causes will be meaningful and significant. Trial courts are likely to and should impose real limits on expert opinions regarding "possible" alternative causes under well-settled California law. In establishing limits on speculative or conjectural opinions, Kline cited Sargon Enters. Univ. of S. Cal. (2012) 55 Cal. 4th 747. In Sargon, the California Supreme Court held that expert opinions should be excluded under two potential circumstances: when they are based on either (1) assumptions of fact without evidentiary support or (2) on "speculative or conjectural factors." Sargon, 55 Cal. 4th at 770. Therefore, an expert cannot opine that plaintiff's injuries could possibly be due to obesity, smoking, or asthma if the record does not support the factual predicates that the plaintiff is obese, does smoke, or has asthma. Nor can an expert reach a conclusion in reliance on "speculative factors" without support in reliable scientific principles. The case of Sanchez v. Kern Emergency Medical Transp. Corp. (2017) 8 Cal. App. 5th 146 (2017) demonstrates both types of speculation. The Court of Appeal excluded the declaration of plaintiff's neurosurgeon expert on both grounds set forth in Sargon. First, the neurosurgeon opined that the delay in transporting the plaintiff to the hospital exacerbated his brain injury, but the Court of Appeal found the evidentiary record did not support any opinion of undue delay. Id. at 158. The Court of Appeal gave a minute-by-minute account to show that the plaintiff could not have gotten to the hospital any sooner than factually occurred. Second, the Court of Appeal found that plaintiff's neurosurgeon applied a speculative principle to conclude that a delay of less than 30 minutes exacerbated his injuries. Specifically, the Court of Appeal cited the defense expert's declaration that there is no medical principle based on his review of "the world's research literature" that "faster is better" or that "delays in treatment in the range of 0 to 30 minutes affect patient outcomes" for plaintiff's injuries. Sanchez is a case showing the two ways expert opinions can be speculative: the expert reaches a conclusion by assuming a fact or by applying a principle without substantiated support in the scientific literature.

Finally, while Kline has impacted the landscape of the nature of rebuttal expert opinions, it is not clear that the California Supreme Court will adopt the Kline rule. Other Courts of Appeal have essentially concluded that any expert opinion based on possibilities is by definition speculation. Jones v. Ortho Pharm. Corp. (1985) 163 Cal. App. 3d 396, 403-404 ("For to the scientific mind, all things are possible. And with all things possible, citizens would have no reasoned protection from the speculations of courts and juries."). Until the Supreme Court rules, trial courts will need to strike the right balance between "possible" causation opinions by defense experts and speculation and conjecture.