FORD MOTOR COMPANY
IN THE COURT OF SPECIAL APPEALS
September Term, 2011
Plaintiffs expert [Dr Welch] on causation asserted:
“every exposure to asbestos is a substantial contributing cause and so brake exposure would be a substantial cause even if [the plaintiff] had other exposures.” On cross-examination, Dr. Welch further explained her opinion that every exposure to asbestos is a “substantial contributing cause” of mesothelioma.
The judgment analyses this as follows:
Where the question of causation is probabilistic:
- “substantiality” and “responsibility” necessarily imply some test of magnitude, viz., how much must exposure have increased one’s risk of harm in order to hold the responsible party liable?
- “substantiality” is essentially a burden of proof
For reasons we need not explore in detail, it is not prudent to set a singular minimum “relative risk” value as a legal standard.
The judgment refers to the problem, namely, that if an opinion that every exposure is substantial “is sufficient for plaintiff to meet his burden, the ‘substantial factor’ test would be meaningless; the objection is that expert testimony cannot render a legal test meaningless.
By way of guidance for a subsequent action, the court offers some more structured argument that could inform the trier of fact:
Dr. Welch could have taken appellants’ allegations as hypothetical facts and estimated the likelihood that Mrs. Dixon suffered various exposures to asbestos, as well as the likely risks attendant to those possible exposures taken from epidemiological studies.
Armed with expert estimates, rendered with reasonable certainty, the jury could then have weighed the evidence to determine whether the factual foundations and methods of the risk estimate were sound and whether the resultant risk was “substantial.”
The court explains that the evidence that had been presented in this case was not up to mark:
Instead, Dr. Welch’s opinion merely implied that there was some non-zero probability that Mrs. Dixon was exposed to asbestos from Ford’s products, and that this resulted in some non-zero increase in her risk of contracting mesothelioma.
Dr. Welch provided no information that could help the finder of fact to decide whether the elevated risk in this case was “substantial.”
Thus, whatever information Dr.Welch conveyed could not possibly have helped the jurors to weigh the substantiality of Ford’s contribution to Mrs. Dixon’s disease.
Having erroneously gained the court’s imprimatur of expert testimony, Dr. Welch’s unhelpful opinion was prejudicial to Ford and demands a new trial, either without her opinion on substantiality or else with some quantitative testimony that will help the jury fulfill its charge.
- The judgment confirms the requirement that the plaintiff must bear the burden of proof.
- Substantiality will be an important test in these cases.
- The trier of fact, not the expert, decides what is substantial and what is not substantial.
- In order to do so, they need to be appropriately informed, taking as fact those facts they prefer.
- There are clear rules on scientific testimony.
In this case, the main problem was that the trier of fact had not been put in a position to decide whether or not the exposure to asbestos was substantial. The decision made in the first hearing was therefore unsound. There was no view as to whether the earlier decision was right or wrong.
Having heard a best estimate of the additional risk involved, even if minuscule, the trier of fact could still quite correctly decide, at a subsequent trial, that this risk was substantial. There is, as yet, no legal threshold that allows science to inform as to whether something is substantial or not, that is a matter for legal judgment alone. And so it should be.
But triers of fact need more help in deciding such facts.
In my opinion, the first thing is to decide if additional risk exists or not. This point still seems to have escaped the court on this occasion, distracted as they were by the word ‘substantial’ and the need to defend their right to decide it.
An objective test of factual evidence would be useful.
Experts can properly testify as to the probability that the measured risk in one situation [living in a typical urban environment] is different from the measured risk in another situation [living in a typical urban environment and being married to a car mechanic]. To do this they need to know:
- levels and precisions concerning dust exposure, and
- the right choice of epidemiological evidence
These are facts that the court can choose, and are the same facts that will be called for at a subsequent trial in this particular case.
The key is not to charge straight into an argument about how big the seeming difference is. The key is to first determine whether or not the two risks are different. Science has been answering this probability of difference question for at least 200 years; it is not difficult ground. An Expert who cannot make this assessment, is probably an Expert in other things.
- If the probability of there being a difference in risk exceeds 50% then the two risks are different.
- If the probability of there being a difference is below 50% then the two risks are the same.
Once shown to be different, the jury or trier of fact can then tackle the question as to whether the additional risk was substantial. But, if they are not different, then there is no case to answer. The end.
One very appealing feature of this approach is that it will very quickly become apparent that there is a minimum level of allegedly negligent exposure before two such risks can be found to be different. De minimis exposure can be defined without imputing any judgement at all as to the meaning of the word substantial. Substantial would be the court’s prerogative once the Plaintiff had shown that there was a fact worthy of attention.
Another very appealing feature is that once the exposure and epidemiological data have been chosen, all competent experts will report the same probability of difference. It is not a question of judgement.