Merit Affidavits and Causation

February 28, 2014

Idaho is one of many states that require plaintiffs to accompany suits against doctors by expert affidavits. An affidavit must verify the plaintiff’s allegations about the doctor’s substandard treatment that caused him injury. The Idaho Supreme Court has recently applied this requirement in Nield v. Pocatello Health Services, — P.3d —, 2014 WL 585944 (Idaho 2014).

This case involved a plaintiff who filed a suit against medical center in which she complained about negligent wound care and unsanitary conditions that resulted in the amputation of her leg. An expert affidavit filed with that suit opined that the center’s negligence was responsible for the plaintiff’s injury. The plaintiff’s expert, however, failed to address alternative causes of the injury that the defendant and its expert claimed to be dominant. These causes included the plaintiff’s preexisting medical conditions.

The Idaho Supreme Court ruled that the affidavit nonetheless makes a prima facie case for the plaintiff. The Court observed that the plaintiff’s expert did not follow – and did not have to follow – the differential etiology method that involves “an analysis of all hypotheses that might explain the patient’s symptoms or mortality. After identifying all of the potential causes of symptoms, the expert then engages in a process of eliminating hypotheses in order to reach a conclusion as to the most likely cause.” The Court explained that when a plaintiff files an expert affidavit that relies on differential etiology, the trial court would be “justified in excluding the expert’s testimony if the expert fails to offer an explanation why an alternative cause is ruled out.” However, the Court clarified in this connection that “Differential diagnosis is merely an alternate means of establishing causation where there are several potential causes of symptoms and there is insufficient scientific basis to conclusively establish any one potential cause. Where a specific cause of a patient’s symptoms can be stated to a reasonable medical certainty, there is no place for this alternate means of establishing causation.” Consequently, a plaintiff’s expert only needs to show that the defendant’s malpractice was among the potential causes of the injury. This showing, held the Court, should move the plaintiff’s case to the jury.

This decision is correct. The plaintiff’s expert fully verified her allegations of malpractice against the defendant. The expert could not conclusively verify the requisite causal nexus because of the plaintiff’s preexisting medical condition. This problem is systemic and well-known: patients with serious preexisting conditions are generally unable to causally associate their injuries to their doctors’ malpractice. Aware of this problem, courts across the nation have designed special rules that allow wronged patients to recover compensation even when they are unable to prove causation by a preponderance of the evidence. Those rules prevent malpractitioners from finding refuge in the causal indeterminacy of their victims’ injuries. Under those rules, differential etiology is one of several methods of proving causation. This method is optional and plaintiffs are free to use alternative methods.

The Idaho Supreme Court thus continued the nationwide policy of narrowing malpractitioners’ exits from liability. This policy interplays with the stringent procedural and evidentiary requirements that narrow doctors’ entry into liability for equally good reasons. See here. The expert’s affidavit, as I already mentioned, have satisfied these requirements.