Christophersen's (P) decedent died from a rare form of colon cancer. Before he died, he was employed by Marathon (D). While employed by D, P's decedent was exposed to battery manufacturing fumes. P claimed that his cancer was caused by exposure to these fumes. P relied solely on the expert testimony of Dr. Miller to establish causation. The district court, excluding this expert testimony as unreliable, granted D's motion for summary judgment on a theory of insufficient evidence of causation. P appealed, and the summary judgment was reversed. D was granted a rehearing.