If you don’t know where a line is, you can’t say whether someone has crossed it. That principle applies in spades to expert witnesses, particularly when their role in the case calls on them to help the jury understand where the lines are drawn in their field. Thus, for example, a toxicology expert who cannot say how much chemical exposure is required to produce a toxic effect cannot opine that the plaintiff’s exposure was sufficient to cause that effect. Likewise, an expert who criticizes a product’s warnings but cannot articulate an adequate warning does not pass muster under Federal Rule of Evidence 702. See, e.g., Bourelle v. Crown Equip. Corp., 220 F.3d 532, 538-39 (7th Cir. 2000).
The Seventh Circuit recently gave yet another illustration of this principle at work. In Burns v. Sherwin-Williams Co., — F.4th —, 2023 WL 5210857 (7th Cir. 2023), a plaintiff truck driver was injured while making a delivery at defendant’s store using a “walkie” (i.e., an electric forklift that the operator walks behind) owned by defendant. Plaintiff was backing the walkie down a ramp and toward a dumpster with pallets laying on the ground nearby. Unfortunately, he underestimated the walkie’s stopping distance. He tried “plugging” – i.e., pushing the thumb switch in the opposite direction to slow and then reverse the walkie – and then engaged the emergency brake, but it was too late. He trapped his foot against the pallets, then fell over and broke his ankle.
Plaintiff sued defendant, alleging negligence in leaving the pallets lying on the ground and in providing an unsafe walkie. In support of his claim that the walkie was unsafe, he proffered an expert witness who opined that the walkie failed to stop fast enough and that the pallets had been stored too close to the ramp. Defendant moved to exclude plaintiff’s expert and for summary judgment. The district court granted both motions, holding that defendant owed no duty regarding the pallets because they were an open and obvious condition and also holding that plaintiff’s expert testimony was unreliable and, therefore, inadmissible.
The Seventh Circuit affirmed. Although one judge dissented as to whether the “open and obvious danger” doctrine should apply, the panel unanimously agreed that the district court had properly excluded plaintiff’s expert’s opinions. His first opinion – that the walkie failed to stop fast enough – was based on a test he had run in an effort to mimic the accident conditions. He ran that test four times, observing that the walkie stopped “in an appropriately quick manner” twice but took “approximately 60 to 64 inches” to stop in the other two runs. He opined that this evidenced a defect in the walkie. However, he could not identify any relevant industry standard or language in the product’s manual as to how fast a walkie should stop under such conditions. The manual noted that a fully loaded walkie should stop within 68 inches after braking, but it was silent as to how fast a walkie should stop when plugging or when not fully loaded. As the Seventh Circuit explained, “[t]he issue is not that [the expert] fails to support some arbitrary line that he has drawn, but that [he] cannot even say where to draw it. He simply claims that wherever that line may be, 60 to 64 inches is on the wrong side.” Notably, although the Seventh Circuit’s opinion does not mention it, plaintiff had argued in both the district court (2022 WL 18457588) and in the Seventh Circuit (Case No. 22-2825, Doc. No. 16) that his expert’s failings “go to the weight of the testimony, not the admissibility.” The Seventh Circuit tacitly rejected that argument, holding that the expert had offered “a bare conclusion which was properly excluded.”
The expert’s second opinion – that defendant had not kept its premises in a reasonably safe condition because the discarded pallets were too close to the ramp – was “entirely unhelpful because a factfinder is equally able to assess the risk posed by the pallets.” Thus, the Seventh Circuit affirmed exclusion of that opinion as well.
Burns is the latest in a line of cases that apply variations on a simple, common-sense theme – an expert who cannot articulate the applicable standard should not be allowed to opine that a defendant failed to meet the applicable standard. Such testimony is not a “shaky but admissible” opinion to be attacked on cross-examination; it is internally inconsistent, is inherently unreliable, and should be excluded under Rule 702.