Challenging Causation in Environmental Cases

In late 2008, the Centers for Disease Control and Prevention (“CDC”) confronted an impending public health crisis. One hundred sixty-six people were hospitalized with salmonella-related illnesses. Dr. Ian Williams, Outbreak Response Branch chief at CDC, headed an investigation that identified Peanut Corporation of America’s (“PCA”) King Nut peanut butter as the source of the salmonella outbreak. An ensuing federal investigation resulted in conspiracy, fraud, and obstruction of justice charges against several PCA executives and employees. See United States v. Parnell, No. 1:13-CR-12 (WLS), 2014 WL 4388523 (M.D. Ga. Sept.5, 2014).

When the government indicated that Dr. Williams would provide expert testimony at trial that the King Nut peanut butter caused the outbreak, the defendants moved to exclude his testimony. Id. at *1. Defendants sought to prevent Dr. Williams from testifying that (1) illnesses were caused by salmonella, and (2) for every reported case of a salmonella-related illness, there was likely an additional 30 unreported cases. Id. at *2. Defendants offered two exclusion theories at a Daubert hearing. First, they argued that the probative value of the evidence was substantially outweighed by the danger of unfair prejudice and should be excluded under Federal Rule of Evidence 403. Id. Second, they argued that the Confrontation Clause barred Dr. Williams’s testimony because he relied on information gathered and developed by others. Id. at *3, *5. The court rejected both arguments and denied the motion to exclude. Id. at *1. A jury subsequently returned a guilty verdict.

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