BRIAN MILWARD and LINDA J. MILWARD, Plaintiffs, Appellants,
RUST-OLEUM CORPORATION, Defendant, Appellee.
APPEAL FROM THE UNITED STATES DISTRICT COURT FOR THE DISTRICT OF MASSACHUSETTS [Hon. Douglas P. Woodlock, U.S. District Judge]
Steve Baughman Jensen, with whom Allen Stewart, P.C., Ian McCallister, and Kreindler & Kreindler, LLP, were on brief, for appellants.
Francis M. Lynch, with whom Cetrulo LLP, was on brief, for appellee.
Before Howard, Chief Judge, Thompson, Circuit Judge, and Laplante [*] District Judge.
HOWARD, Chief Judge.
In this toxic tort case, we previously considered the admissibility of testimony from the plaintiffs' general causation expert. At issue in the present appeal is whether the district court abused its discretion in excluding the testimony of the plaintiffs' specific causation expert. We conclude that the district court's ruling was a supportable exercise of its discretion, and we therefore affirm the grant of summary judgment to the defendant following that evidentiary ruling.
Brian Milward worked as a pipefitter and refrigerator technician for over thirty years. During the course of his employment, Milward was exposed to varying levels of benzene from paints and other products manufactured by (among others) Rust-Oleum Corporation. In 2004, he was diagnosed with Acute Promyelocytic Leukemia ("APL"). Three years later, Milward and his spouse sued a number of defendants on the theory that their negligence caused Milward's disease. The only remaining defendant is Rust-Oleum.
To succeed against Rust-Oleum, the Milwards had the burden of establishing, through expert testimony, general and specific causation. In other words, they needed to show that exposure to benzene can cause APL (general causation), and that exposure to benzene was, in fact, a substantial factor in the development of Brian's APL (specific causation). The district court bifurcated the proceedings; it planned first to address the admissibility of expert testimony on general causation, and then to consider the specific causation issue.
In a 2009 ruling, the district court excluded the Milwards' general causation expert. Accordingly, it entered judgment in favor of the defendants without proceeding to the second phase of the case. The Milwards appealed that decision and, for reasons specific to their general causation expert, we reversed. See Milward v. Acuity Specialty Prods. Grp., Inc., 639 F.3d 11 (1st Cir. 2011) . We remanded the case to the district court to proceed to the specific causation question.
Under the supervision of a different district court judge, the parties engaged in discovery on the subject of specific causation. Relevant here, the Milwards retained occupational medicine physician Dr. Sheila Butler to serve as their expert witness. The admissibility of her opinion testimony is at the heart of this appeal, and thus additional background on her opinion is in order.
Dr. Butler, an employee of the Veterans Administration, specializes in clinical assessments of environmental and occupational exposure in combat-exposed veterans. In her proposed testimony, Dr. Butler presented three theories.
First, she testified that although benzene is naturally occurring, there is no safe level of benzene exposure. This was her predominant theory, and she consistently reiterated her hypothesis. She emphasized that she reached this conclusion by examining "the biology, the pathophysiology, what the substance does to the person and the disease process." And, she noted, she was able to do so without relying on any of the relevant epidemiological studies. Given this no-safe level theory, Dr. Butler maintained that Milward's exposure (as detailed by Dr. Stewart) was likely the cause of his APL. The district court rejected this hypothesis because it could not be properly tested with any known rate of error. The Milwards do not meaningfully challenge the district court's conclusion on appeal. Accordingly, we assume that the ruling was correct and bypass further discussion of the issue. See Mills v. U.S. Bank, NA, 753 F.3d 47, 55 (1st Cir. 2014) .
Second, Dr. Butler rather cursorily concluded that even beyond the no-safe level hypothesis, certain epidemiological studies have established that an individual's "relative risk" of developing APL increases when exposed to specified amounts of benzene. She then compared Milward's exposure levels to those that had been found to be dangerous in that research. Since Milward's exposure was higher than the amounts found to be hazardous, Dr. Butler reasoned that benzene exposure was likely the cause of his APL. Notably, she did not explain why she chose the studies on which she relied, nor did she address any study with contrary findings. In fact, during Dr. Butler's deposition, defendant's counsel asked her a number of questions about her ability and willingness to engage with the relevant epidemiological research. For instance, counsel asked, "Are you aware of any studies which find that there is no relationship between benzene exposure and APL, " to which she answered "Yes . . . the literature  has support for both." Counsel then asked, "Do you intend in this case to weigh the different epidemiological studies and offer an opinion as to which ones we should rely on and which ones we should discount, " to which she replied, "No."
Finally, Dr. Butler engaged in a "differential diagnosis" to conclude that benzene exposure likely caused Milward's APL. Through this method (essentially a process of elimination) Dr. Butler "ruled out" some of the more common factors associated with APL, among them obesity and smoking. She then determined that since benzene exposure was a potential cause, she could also "rule out" an idiopathic diagnosis (or, a diagnosis without a known cause). Thus, since benzene exposure was the only significant potential cause remaining, she concluded that it was likely the culprit.
Back in court, Rust-Oleum moved both to exclude Dr. Butler's testimony and for summary judgment. The district court evaluated, and rejected, each of the theories that Dr. Butler put forward to establish specific causation. For reasons discussed below, the judge ultimately ruled that Dr. Butler's testimony was inadmissible under Federal Rule of Evidence 702. Since the Milwards could not establish specific causation without Dr. Butler's testimony, the district court granted summary judgment in favor of Rust-Oleum. Fed.R.Civ.P. 56. This timely appeal followed.
We review the district court's decision to admit or exclude expert testimony for abuse of discretion. See United States v. Shay, 57 F.3d 126, 132 (1st Cir. 1995) (noting that we will only "reverse a decision ... if (1) the district court based the decision on an incorrect legal standard ... or (2) we have a definite and firm conviction that the court made a clear error of judgment. . . .")• Predicate factual findings are reviewed for clear error, while pure questions of law engender de novo review. Milward, 639 F.3d at 13-14. As for the district court's ultimate decision to grant Rust-Oleum summary judgment, because the Milwards are proceeding under state-law theories of liability, we apply Massachusetts law, see Philibotte v. Nisource Corp. Servs. Co., 793 F.3d 159, 165 (1st Cir. 2015), and review the decision de novo, see Samaan v. St. Joseph Hosp., 670 F.3d 21, 38 (1st Cir. 2012) .
As in the district court, our admissibility inquiry is guided by Federal Rule of Evidence 702, which provides that:
A witness who is qualified as an expert by knowledge, skill, experience, training, or education may testify in the form of an opinion or otherwise if:
(a) the expert's scientific, technical, or other specialized knowledge will help the trier of fact to understand the evidence ...