We previously blogged about a decision in the In re Deepwater Horizon BELO litigation – Ruffin v. BP Exploration & Production, Inc. – in which the Fifth Circuit affirmed summary judgment for defendants in an alleged chemical exposure case based solely on exclusion of the plaintiff’s expert testimony on general causation without reaching the experts’ specific causation opinions. As it turns out, in another BELO case argued before the same panel on the same day, the panel analyzed the plaintiff’s experts’ specific causation opinions and declined to reach their general causation opinions. Williams v. BP Exploration & Production, — F.4th —, 2025 WL 1904153 (5th Cir. July 10, 2025). Notwithstanding the concerns we previously expressed about the Ruffin panel’s approach to general causation in isolation from specific causation, the Ruffin and Williams decisions provide a potent couplet illustrating that general causation and specific causation are two distinct steps in the analysis. Both must be proven in order for a plaintiff to make a prima facie case.
The plaintiff in Williams had worked cleaning up after the Deepwater Horizon oil spill and was diagnosed shortly thereafter with chronic pansinusitis. He sued, claiming he developed the condition from his exposure to oil, dispersants, and other chemicals during his cleanup work. He disclosed two experts, each of whom authored a report on causation. Defendants moved to exclude both experts and, later, moved for summary judgment for lack of admissible evidence establishing causation. The district court granted the motions, and the plaintiff appealed.
As in Ruffin, the panel affirmed the district court’s decisions. But the panel approached Williams in reverse, addressing the experts’ specific causation opinions without reaching general causation. The first expert purported to apply a differential etiology approach in his specific causation opinion, but the district court had found that opinion unreliable because he “did not describe any attempts to evaluate whether any of the potential alternative causes he lists could have caused” the plaintiff’s condition. The plaintiff argued the expert was not obligated to “exhaustively include every possible detail” and that his simple statement the plaintiff had no “significant medical problems prior to his employment” was sufficient. The Williams panel disagreed, holding the relevant section of the report, which contained only “three sentences, and with zero analysis,” was insufficient to support reliable application of a differential etiology.
As for the second expert, the district court had found both procedural and substantive concerns with his report. First, the report was “facially suspect” because it used the wrong plaintiff’s name six times, bringing the accuracy of all the findings in the report into question. Second, according to the information on which the expert based his own general causation opinion, he agreed the plaintiff’s risk for non-cancer conditions, including pansinusitis, was “100 times lower than what the EPA deems acceptable.” Finally, even this low-risk calculation was based on the incorrect assumption that benzene concentrations were twice as high as the data indicated. The plaintiff argued the expert’s opinion was supported because he testified that an exposure below the threshold level “doesn’t mean . . . that adverse events cannot happen.” The Williams panel held otherwise, noting at the outset that the reliability of the expert’s opinions was called into question by the fact that his report appeared to have been initially prepared for another plaintiff and contained erroneous assumptions about exposure levels. Further, the expert failed to resolve his finding that the plaintiff’s exposure was 100 times lower than acceptable and yet must have caused his condition. Thus, the Williams panel found the district court did not abuse its discretion in excluding both reports.
Despite citing precedent that “sequence matters” and “a plaintiff must establish general causation before moving to specific causation,” the Williams panel held that the plaintiff’s experts’ failure to establish specific causation doomed his case and therefore “decline[d] to reach the question of general causation.” Having affirmed the district court’s exclusion of both experts’ specific causation opinions, the panel likewise affirmed the grant of summary judgment to the defendants.
Ruffin and Williams are two opinions from the same set of three Fifth Circuit judges, both from the BELO litigation and both argued on the same day. In Ruffin, the panel addressed general causation but not specific causation. In Williams, the panel did the exact opposite. And in both cases, the lack of one half of the causation equation proved fatal to the plaintiff’s claim. The pair of decisions serves as a reminder that a plaintiff’s case is only as strong as the weakest link in their theory of causation.
The material contained in this communication is informational, general in nature and does not constitute legal advice. The material contained in this communication should not be relied upon or used without consulting a lawyer to consider your specific circumstances. This communication was published on the date specified and may not include any changes in the topics, laws, rules or regulations covered. Receipt of this communication does not establish an attorney-client relationship. In some jurisdictions, this communication may be considered attorney advertising.
