The general rule in most jurisdictions is that where injury is caused by exposure to some substance, the plaintiff has the burden of proving both General causation and Specific causation. General causation means there is sufficient scientific evidence to prove that the substance is capable of causing the alleged injury; Specific causation means there is sufficient evidence that the Plaintiff was actually exposed to the substance in a manner that could have caused the injury (i.e., the exposure route and quantity of exposure known to cause that type of injury actually occurred).

We often see cases where the plaintiff’s expert claims proof of specific causation through the use of “differential diagnosis.” This most often occurs where the expert is a physician. However, in Higgins v.  Koch Development Corporation, a Seventh Circuit case filed yesterday (Case # 14-2207, filed 7/20/15 – search for it here, for now), the Court explained why this method doesNOT meet the Specific causation requirement:

“[T]he record is silent on whether Dr. Haacke considered other possible causes of [Plaintiff]’s ailments and, if so, how and why she ruled them out. That is problematic, because [Plaintiff] told the district court that Dr. Haacke had assessed the cause of his ailments by employing “differential diagnosis.” “Differential diagnosis” actually refers to a method of diagnosing an ailment, not determining its cause. “Differential etiology,” on the other hand, is a causation‐determining methodology. But, to be validly conducted, an expert must systematically “rule in” and “rule out” potential causes in arriving at her ultimate conclusion.” [citations omitted]

There is caselaw to the same effect in other jurisdictions, but attorneys who are not familiar with toxic tort claims may not appreciate or understand the distinction. It is important to recognize the causation issues early in toxic tort claims so that discovery and development of the case facts are conducted within the framework of the standards for admissibility.

Speaking of doctors (for those of you used to some levity in these posts), at my age, when someone asks to “play doctor,” they plan to just make me wait 45 minutes and then double-bill the insurance company.