Expert reports are common in scientifically complex cases. Every practitioner, regardless of experience level, must read an expert's report carefully before production. A recent opinion from the Fifth Circuit serves as a cautionary tale against using sloppy expert reports that are fatal to a party's claim or defense, in this case, the plaintiff.
In Williams v. BP Exploration & Production, Inc., et al,1 the United States Court of Appeals for the Fifth Circuit recently affirmed a district court's exclusion of expert testimony and the subsequent grant of summary judgment in favor of defendants. The plaintiff, Matthew Williams, sued for bodily injuries sustained when he performed oil spill clean-up work in the Gulf of Mexico after the British Petroleum Deepwater Horizon oil spill in 2010. A decade later, in 2020, Williams was diagnosed with chronic pansinusitis, a long-term inflammation of the nasal sinuses and linings of the nasal passages. Williams alleged that his chronic condition resulted from exposure to oil, dispersants, and other chemicals during the cleanup work and filed suit against defendants-appellees, BP Exploration & Production, Inc. and BP America Production Co. (collectively, "BP") under the Back-End Litigation Option (BELO) provisions of the class action settlement relating to the oil spill.
To establish causation, Williams offered the testimony of two expert witnesses to link his chronic pansinusitis diagnosis to his exposure as an oil-spill cleanup worker: Dr. Michael Freeman2 and Dr. James Clark. BP moved to exclude both expert reports under Federal Rule of Evidence 702 and Daubert, followed by a motion for summary judgment based on the lack of admissible expert testimony needed to establish specific causation. The district court granted all of BP's motions, and the Fifth Circuit seeking affirmed.
The Fifth Circuit found Dr. Clark's testimony unreliable. Dr. Clark's report repeatedly referred to a different plaintiff, a "Mr. Vincent" instead of "Mr. Williams, six different times, suggesting the report had been repurposed from another case. This prompted the Fifth Circuit to question how carefully Dr. Clark had prepared and reviewed his report, and whether other information in his report was likewise inaccurate. Importantly, Dr. Clark's report contained a significant factual error—he overestimated Williams' benzene exposure by twice the actual amount, according to data published by the Environmental Protection Agency. These errors seriously undermined the reliability and factual accuracy supporting Dr. Clark's conclusions concerning the specific causation of Williams' injuries. Accordingly, the Fifth Circuit affirmed the district court's judgment, noting that Williams had failed to rebut the reasons for exclusion or to demonstrate that the district court had abused its discretion in granting BP's Daubert motion to exclude Dr. Clark.
The Williams v. BP case is important for several legal and practical reasons. First, this case underscores the critical role of Federal Rule of Evidence 702 and the Daubert standard. The Fifth Circuit reaffirmed that expert testimony must be based on reliable methods and applied properly to case facts. Merely asserting a causal link, without rigorous analysis, is not enough—especially in scientifically complex cases. This decision reinforces the judiciary's "gatekeeping" function, and courts will closely scrutinize expert methodologies and factual accuracy.
Second, and most importantly, the exclusion of Dr. Clark's testimony, partly due to clerical errors, serves as a cautionary tale to all practitioners. Even seemingly minor cut-and-paste mistakes can undermine the credibility of expert opinions, which can result in exclusion and case dismissal. Expert reports should be specifically tailored for the case at hand and reviewed carefully for factual accuracy. This case emphasizes the need for rigor and precision in preparing expert reports in litigation
Footnotes
1. Williams v. BP Exploration & Production, Inc., et al, --- F. 4th --- (5th Cir. 2025), 2025 WL 1904153.
2. For the purpose of this article, we will only be discussing the expert report of Dr. James Clark.
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