Back when we taught Products Liability in law school, one of the topics that always got significant attention and discussion from the bright-eyed students was how to define "defect." The panoply of tests for defective or unreasonably dangerous products never failed to excite discussion, particularly the role of consumer expectations in product assessment.

That same topic is the focus of an interesting recent decision in the Seventh Circuit. See Show v. Ford Motor Co., Nos. 10-2428 and 10-2637 (7th Cir.,  9/19/11).

Plaintiffs were involved in a motor vehicle accident in a 1993 Ford Explorer;  they sued Ford, alleging design defect. In products liability cases in which the plaintiff alleges a design defect, Illinois (whose law supplied the substantive rules) permits the claim to be established in either of two ways. First, the plaintiff may introduce evidence that the product failed to perform as safely as an ordinary consumer would  expect when used in an intended or reasonably foreseeable manner. This has come to be known as the consumer expectation test. Second, the plaintiff may introduce evidence that the product’s design proximately caused his injury, when the benefits of the challenged design do not outweigh the risk of danger inherent in such design. This test, which adds the balancing of risks and benefits to the alternative design and feasibility inquiries, has come to be known as the risk-utility or risk-benefit test.

Here, plaintiffs proceeded under the first prong, and offered no expert opinion. Ford moved for summary judgment in light of the absence of expert testimony. Plaintiffs conceded that testimony by an engineer or other design expert was essential when a claim rests on the risk-utility approach. But, they argued that jurors, as consumers, can find in their own experience all of the necessary opinions under the consumer expectation test. The district court sided with the defense, and plaintiffs appealed.

The court first discussed a very interesting preliminary question. The parties assumed, as did the lower court, that state law in this diversity case determined whether expert testimony was essential. The assumption rested on a belief that the quality of proof is part of the claim’s substantive elements, which in turn depend on state law under the Erie doctrine even when substantive doctrine is implemented through federal evidentiary rules.  However, there was a question whether Illinois treats the risk-utility and consumer expectations approaches as distinct substantive law doctrines, or merely as procedural aspects of the general question: is the product unreasonably dangerous. Perhaps the two tests are not theories of liability; they could be considered methods of proof by which a plaintiff may demonstrate that the element of unreasonable dangerousness is met.  If the consumer expectation test is not an independent theory of liability, perhaps federal rather than state law determines whether expert evidence is essential on it. Federal law often requires expert evidence about consumers' knowledge and behavior, because jurors are supposed to decide on the basis of the record rather than their own intuitions and assumptions. If federal courts require expert evidence, rather than relying solely on jurors' experience, in trademark and credit suits, for example, why not in product defect cases, asked the court?  But the court decided to bypass the question, in light of the parties' positions below. 

Turning to the consumer expectations issue, the court felt that plaintiffs’ argument that jurors should be able to rely on their own expectations as consumers reflected a belief that “expectations” are all that matters. Yet because the consumer expectations approach is just a means of getting at some of the issues that bear on the question whether a product is unreasonably dangerous, it is impossible to dispense with expert knowledge, concluded the panel.  The design defect is tied up in the issue of causation. Did the design decisions that went into the 1993 Ford Explorer even contribute to the rollover? Causation is a question about physics, and design options are the province of engineers. Jurors own cars, but people own lots of products without being able to explain (or even understand) the principles behind their construction and operation.  Unguided intuitions will not solve the equations. Without an expert’s assistance the decision would depend on speculation, which cannot establish causation—an issue on which plaintiffs bear both the burden of production and the risk of non-persuasion.

Because consumer expectations are just one factor in the inquiry whether a product is unreasonably dangerous, a jury unassisted by expert testimony would have to rely on speculation. The record here did not show whether 1993 Explorers were unduly (or unexpectedly) dangerous, because the record (absent an expert) lacked evidence about many issues, such as: (a) under what circumstances they roll over; (b) under what circumstances consumers expect them to do so whether it would be possible to reduce the rollover rate; and (d) whether a different and safer design would have averted this particular accident. All of these are subjects on which plaintiffs bear the burden of proof. There are other issues too, such as whether the precautions needed to curtail the rate of rollovers would be cost-justified.

The absence of expert evidence on these subjects was fatal to plaintiffs’ suit.