The Oregon Supreme Court has released a fascinating opinion on expert testimony.
The Court stated that the Plaintiff
experienced symptoms of pain, swelling, and discoloration in her left hand immediately after injection of a chemical called gadolinium; her pain and the discoloration have continued. At trial, plaintiff proffered the testimony of a medical expert that the gadolinium, instead of going into the vein, went into an area of her hand outside the vein, a circumstance known as "extravasation." As a result, according to the expert, the toxicity of the gadolinium caused both her immediate and her ongoing symptoms. Defendants objected to the expert’s proffered testimony, and the trial court ruled that the testimony did not meet the legal standard for scientific validity. The Court of Appeals affirmed.
A majority of the Court of Appeals excluded the testimony on this basis:
[T]the expert had failed to identify a scientifically valid cause of the injury — one that linked plaintiff’s exposure to gadolinium to the vasospastic disorder that she experienced. In particular, the court noted that the expert had failed to show, either through studies showing a high degree of correlation between gadolinium exposure and the kind of injury that plaintiff had suffered or through a scientifically demonstrable mechanism of causation, that the gadolinium extravasation could have caused plaintiff’s vasospastic disorder.
The Supreme Court reversed, saying that the expert could utilize a differential diagnosis analysis to reach a conclusion as to what probably caused the plaintiff’s injury. It explained as follows:
that differential diagnosis of medical causation often cannot lead an expert to conclude, with certainty, that event "A" caused condition "B." Rather, in many cases, a number of potential causes will be "ruled in," each of which has some percentage of likelihood of having caused plaintiff’s condition; then the expert, by physical examination, testing, or other scientifically valid process, eliminates one or more of the potential causes in an effort to identify the actual cause. Even if the expert is not able to eliminate all alternative causes, the testimony nevertheless may be reliable and admissible if sufficient potential causes are eliminated for the expert to identify one particular cause as the likely cause of the condition. See Note, Navigating Uncertainty: Gatekeeping in the Absence of Hard Science, 113 Harv L Rev 1467, 1474 (2000) (courts generally allow admission of differential diagnosis even when technique has not eliminated all alternative causes). [Footnote omitted.]
It went on to say as follows:
[T]he [intermediate appellate] court disregarded the potential connection between the gadolinium extravasation and plaintiff’s injuries, because, in that court’s view, that potential cause could not be "ruled in." Although the court was properly concerned with avoiding the logical fallacy of post hoc, ergo propter hoc (after this, therefore because of this) reasoning, it failed to give appropriate deference to the expert witness’s reliance upon plaintiff’s sudden, single exposure and her immediate, localized symptoms, as well as to the biological plausibility of the expert’s causation theory. The immediate symptoms that plaintiff experienced in her hand indicate a causal link between the exposure and her symptoms, and her expert’s careful differential diagnosis supports that connection. Moreover, the expert’s reliance on studies demonstrating the toxicity of gadolinium provide a biologically plausible basis for his conclusion. Applying the criteria identified above, we agree with plaintiff that she had made an adequate showing of a scientifically valid basis for "ruling in" gadolinium as a potential cause of her symptoms, as well as for "ruling out" a number of the other possible causes of her injury. The jury should have been permitted to hear the expert’s testimony that, in his opinion, the gadolinium extravasation caused that injury.
There is much, much more to this opinion and those who do medical malpractice work would be advised to read it.
The case is Marcum v. Adventist Health System/West, SC S055431 (OR. Sept. 16, 2008). Read it here.