The Tenth Circuit Court of Appeals has ruled that toxic tort plaintiffs in New Mexico must demonstrate that their alleged injuries would not have occurred “but for” the defendants’ act. Wilcox v. Homestake Mining Co., No. 08-2282 (10th Cir. 9/8/10). The appellate court thereby affirmed the district court’s grant of the uranium-mining mill operators’ motion for summary judgment. Both courts found that plaintiffs failed to show by a reasonable degree of medical certainty that their injuries would have occurred “but for” the release of radioactive substances from defendants’ operations.  

Filed in 2004 by a group of current and former residents of Cibola County, New Mexico, the lawsuit alleged that releases from defendants’ uranium-mining mill caused “injury, illness or death.” Plaintiffs’ experts submitted affidavits asserting that the exposure to radiation from the uranium mill was “a substantial factor” contributing to their illnesses. The trial court and then the appellate court held that the “but for” test and not the “substantial factor” test was the causation standard for toxic tort actions in the state.