Failing to Rule Out Unknown Causes, Expert's Toxic Testimony Tossed

Failing to address unknown causes for a plaintiff's Leukemia in a toxic tort claim, a causation expert witness was reasonably excluded by the trial court, as were the supplemental reports the plaintiff attempted to submit after the plaintiff's witnesses' Daubert hearings, the Tenth Circuit has ruled in Hall v. Conoco (No.17 6086, 10th Cir. 2018), dismissing the plaintiff's appeal.

In Hall v. ConocoPhillips (USDC OK West 2018), Samantha Hall sued ConocoPhillips for negligence and strict liability after being diagnosed with Acute Myeloid Leukemia (AML). Twenty years before the diagnosis, Hall had been a child living near ConocoPhillips's refinery in Ponca City, Oklahoma. She attributed the disease to her early exposure to the refinery's emissions of benzene, a known carcinogen.

To support her claim, Hall engaged three expert witnesses: Dr. David Mitchell, a forensic meteorologist expert witness and air modeler; Dr. Steven Gore, a hematologist/oncologist expert witness; and, Dr. Mary Calvey, an environmental epidemiology expert witness. Mitchell created an air model to estimate benzene concentrations near where Hall had lived, which Gore used to calculate Hall's exposure to benzene and support his opinion that the benzene exposure had caused Hall's disease. Calvey opined similarly.

The district court found that Gore made multiple errors in his expert report. Gore initially declared Hall's Benzene exposure in ppm-years by using the industrial worker's standard (8 hours a day, 5 days a week, 50 weeks a year), but during the Daubert hearing he testified he had been mistaken, that Hall's dose was determined by taking the "[p]eak one-hour exposure" daily for each year of exposure. Gore also mistakenly calculated the number of years of exposure at eight years when Hall had only lived near the refinery for four years.

Gore contended that he had not calculated the benzene exposure but merely added up what was in the expert reports. He admitted that he used the peak one-hour benzene concentration because Mitchell told him that it was the metric used in the industry, but the district court found that insufficient. Mitchell was not a toxicologist or industrial hygenist expert to make that deterimination; it was a decision for the causation expert to make.

Confusion also reigned over Gore's terminology as he opined in his expert report that Hall was exposed to 1.76 ppm-year of Volative Organic Compounds (VOCs including Benzene), but at his deposition, he reduced that exposure level by 20% and set Hall's benzene exposure at 0.3 ppm-year. Then at trial, Gore claimed that he had been misled by ConocoPhillips which had misunderstood Mitchell's air modeling as VOC including benzene when Mitchell had modelled only benzene. He then testified that the original 1.76 ppm-year figure should not have been reduced.

The district court found that Gore's benzene exposure calculations did not satisfy the reliability standards established by Daubert and excluded them.

Even without sufficient evidence of exposure, the district court noted that it "can admit a differential diagnosis that it concludes is reliable if general causation has been established," but the expert must adequately consider and rule out alternative explanations.

Unfortunately, the district court found that Gore did not adequately consider alternative causes for Hall's AML. While Gore admitted that he would consider smoking as a probable cause, he discounted her smoking "after an apparently inadequate investigation of the extent she smoked." More daming to his opinion, Gore also failed to consider unknown causes ("idiopathic causes") for Hall's AML. The court noted unrebutted affidavits from two defense experts that 80-90% of all cases of AML have no known cause. "Courts have repeatedly faulted experts for their failure to consider idiopathic or unknown causes for diseases when rendering their differential diagnoses," the district court wrote. The court found Gore's diagnosis unreliable, excluding his specific causation opinion along with his exposure opinion.

As for Dr. Calvey, she was listed to testify that benzene can cause the specific form of Hall's AML, AML with Inversion 16. During her Daubert hearing, Calvey admitted that she had not searched for peer-reviewed literature linking AML inv(16) with benzene." She defended her methods stating that she "was looking at AML in particular, and most of the studies mention only AML." The district court found that because Calvey "did not acknowledge, account for, or even search for evidence in the relevant scientific literature which refutes her theory," her expert opinion was unreliable, and thus her expert testimony was excluded.

Hall had tried to submit supplemental declarations from Mitchell and Gore, but they were rejected by the court. The submissions came long after the deadline for submitting reports — after ConocoPhillips had filed its Daubert motions. Hall contended that recalculations were necessary because Conoco underreported emissions. The supplemental declarations were based on new information that had been provided to Hall's counsel by Kenneth F. Ede, Ph.D., an environmental scientist. Based on Ede's data, Mitchell made significant changes to the models he had used to assess Hall's exposure to benzene, making a fivefold increase in the emission rate from the refinery.

Conoco raised a threshold objection to the declarations. Hall suggested that Conoco could redepose her experts (and apparently depose her newly added environmental science expert witness, but the district court found that to be too much, stating: "A party may not use the pretext of supplementation to reopen discovery, close gaps in their evidence, and essentially generate new expert reports."

Without the expert testimony of Gore and Calvey, the district court found that Hall lacked the required evidence and granted summary judgment to ConocoPhillips. Hall appealed to the U.S. Court of Appeals for the Tenth Circuit, which concluded that the distict court did not err in excluding the testimony nor in granting summary judgment.

The surprise here is that Hall's counsel was unprepared. Challenging an expert's systematic methodology in ruling out other possible causes of a disease is common in Daubert motions. The precedence was clear. In Henricksen v. ConocoPhillips, 605 F. Supp. 2d 1142 (E.D. Wash. 2009), the plaintiff's causation expert failed to consider and exclude the likelihood that the plaintiff's AML was caused by an unknown factor, and the expert's testimony was excluded. Déjà vu.