Background
Plaintiff Floyd Ruffin worked as a shoreline clean-up worker following the 2010 Deepwater Horizon oil spill. Five years later, he was diagnosed with prostate cancer and sued BP, alleging his cancer was caused by exposure to crude oil and chemicals during the clean-up. Ruffin designated an expert, Dr. Benjamin Rybicki, to testify on causation. Dr. Rybicki concluded that exposure to polycyclic aromatic hydrocarbons, or PAHs, caused Ruffin’s cancer. The district court excluded this testimony under Federal Rule of Evidence seven hundred two and Daubert, finding fatal analytical flaws and an analytical gap between the data and the opinion. The court granted summary judgment to BP. Ruffin appealed.
The court’s reasoning
The Fifth Circuit reviewed the exclusion of expert testimony for abuse of discretion and summary judgment de novo. The court addressed whether an expert must identify a specific quantitative dose of a chemical to establish general causation. The court declined to adopt BP’s proposed rule requiring a specific minimum dangerous dosage, noting that precedent allows for a range of exposure supported by toxicological profiles. However, the court affirmed the exclusion of Dr. Rybicki’s testimony on other grounds. The court found the testimony irrelevant because Dr. Rybicki focused on benzo(a)pyrene as the only PAH confirmed to be carcinogenic, yet neither the expert nor the plaintiff claimed Ruffin was exposed to benzo(a)pyrene specifically. Furthermore, the court found the testimony failed to establish that benzo(a)pyrene causes prostate cancer, as the expert’s evidence primarily linked the chemical to other types of tumors and relied on studies of PAHs generally rather than benzo(a)pyrene specifically. Without admissible expert testimony on general causation, the plaintiff could not meet his burden, and summary judgment was proper.
We decline to adopt such a rule because it conflicts with our precedent. But because we agree with the district court that Ruffin’s expert testimony nevertheless suffers from fatal analytical flaws, we AFFIRM the district court’s exclusion of the testimony and its associated award of summary judgment to BP.
Floyd Ruffin v. BP Exploration & Production, Inc., No. 23-30854, slip op. at 1 (5th Cir. May 27, 2026)
What it means going forward
The decision clarifies that while a specific quantitative dose is not strictly required to prove general causation in toxic tort cases, experts must still provide a reliable link between the specific chemical exposure and the specific injury alleged. It reinforces the requirement that expert testimony must be relevant to the specific facts of the case, particularly regarding the identity of the harmful agent and the specific disease caused.
Podcast (federal-narrative-summaries): Play in new window | Download