You were looking for proof of causation beyond the obvious correlation. (biggerpockets.com)
However, this approach should be rarely used to ensure that the fundamental principles of tort law for proof of causation are not undermined. (slaw.ca)
1See Russelyn S. Carruth and Bernard D. Goldstein, Relative Risk of Greater Than Two in Proof of Causation in Toxic Tort Litigation, 41 Jurimetrics 195 (collecting cases). (genomicslawreport.com)