A case from last week reminds us of the importance of appellate review of expert witness admissibility decisions, and the potential impact of junk science on a jury. See Hyundai Motor Co. v. Duncan, No. 140216 (Va. 1/8/15).

Defendant appealed from a judgment entered on a jury verdict in favor of plaintiffs, and argued that the trial court erred in admitting the opinion testimony of the plaintiffs' designated expert witness. The expert testified that the location of the side airbag sensor in the 2008 Hyundai Tiburon being driven by plaintiff in a single-vehicle accident rendered the Tiburon unreasonably dangerous. The state supreme court agreed and reversed the judgment of the circuit court.

Plaintiffs alleged a design defect. and to support their claim, they designated one Geoffrey Mahon, a mechanical engineer, as an expert in airbag design. Mahon expressed the opinion (just a few details) that if the defendant had located the sensor for the side airbag system on the B-pillar of the vehicle (the pillar where the front door closes), approximately 4 to 6 inches from the floor, instead of on the cross-member underneath the driver's seat, the side airbag would have deployed in this accident. Therefore, according to Mahon, the location of the side airbag sensor on the cross-member allegedly rendered the 2008 Tiburon unreasonably dangerous,

Prior to trial, Hyundai moved to exclude Mahon's opinions as having an insufficient foundation because the witness did not conduct any analysis to determine whether the side airbag truly would have deployed if the sensor had been located where Mahon proposed. When deposed, Mahon had testified that in reaching his opinion, he relied upon a computer-aided engineering study conducted by Hyundai which had analyzed 14 potential locations for the side airbag sensor, but he did not adopt any of the 14 locations analyzed by Hyundai for his placement of the side airbag sensor. He admitted he would have to run more tests to verify his location.  And while Mahon believed the best location for the sensor was at the B-pillar, he testified he did no such testing of his own to determine if the side airbag would have actually deployed in the accident had the sensor been placed at any other location. He was nonetheless permitted to express his opinions at trial, over Hyundai's objections.

The court noted that Mahon's initial impression of the airbag system was that “the airbag should have gone off,” but upon further investigation, he concluded that the system was acting as designed -- a design he said was defective. At trial, Mahon agreed that the 2008 Tiburon, with the existing side airbag system, complied with the federal regulatory standard specifically related to side impact protection. He further acknowledged that the 2008 Tiburon “did reasonably well” when Hyundai conducted 22 crash tests in which it ran the vehicle into different types of barriers, at different speeds and angles. As noted, in Mahon's view, the 2008 Tiburon was nevertheless defectively designed and unreasonably dangerous because the sensor for the side airbag system was not located on the B-pillar. 

Consistent with his deposition testimony, Mahon testified at trial that he did not perform an analysis to determine whether the side airbag in the vehicle would actually have deployed if the sensor was in a different location. Mahon conceded that he had no real data demonstrating the real-world performance of a sensor located on the B-pillar that certain distance from the floor. He further agreed that because the airbag system must work quickly, that is the sensor system must decide within 15 milliseconds of a crash event whether an airbag is required and then inflate the airbag in 15 to 50 milliseconds, the location of the sensor is important to the overall crash sensing system such that inches, and even increments smaller than inches, really matter in the determination of the location of the sensor.

The state Supreme Court noted that expert opinion must be premised upon assumptions that have a sufficient factual basis and take into account all relevant variables. Expert testimony founded upon assumptions that have no basis in fact is not merely subject to refutation by cross-examination or by counter-experts; it is inadmissible. Failure of the trial court to strike such testimony upon a motion timely made is error subject to reversal on appeal. Furthermore, expert testimony is inadmissible if the expert fails to consider all the variables that bear upon the inferences to be deduced from the facts observed. See CNH America LLC v. Smith, 281 Va. 60, 67, 704 S.E.2d 372, 375 (2011).

In short, concluded the court, Mahon's opinion that the 2008 Tiburon was unreasonably dangerous was without sufficient evidentiary support because it was premised upon his mere assumption that the side airbag would have deployed here if the sensor was at his proposed location—an assumption that clearly lacked a sufficient factual basis and disregarded the variables he himself acknowledged as bearing upon the sensor location determination. Although experts may extrapolate opinions from existing data, a trial court should not admit expert opinion which is connected to existing data only by the ipse dixit of the expert. General Elec. Co. v. Joiner, 522 U.S. 136, 146 (1997) (decided under the version of Fed.R.Evid. 702 which the General Assembly adopted, verbatim, in current Va. Code § 8.01–401.3(A)). The expert's opinion that the vehicle was unreasonably dangerous was based on his ipse dixit assumption that the side airbag would have deployed in the crash if the sensor had been located on the B-pillar. But the “analytical gap” between the data Mahon relied upon from Hyundai's location study and the opinion he proffered at trail was simply too great. Therefore, Mahon's opinion was inadmissible, and the trial court abused its discretion in admitting it.

The plaintiffs relied upon Mahon's opinion that the 2008 Tiburon was unreasonably dangerous to satisfy their burden of proving that Hyundai breached its implied warranty of merchantability. Because Mahon's opinion supplied the only support for the claim that the vehicle was unreasonably dangerous, the inadmissibility of Mahon's opinion was as a matter of law fatal to the claim and entitled Hyundai to judgment as a matter of law.