Dave Conley, a longtime heavy smoker, was diagnosed with lung cancer. He died two years later. His death certificate stated that the cause of death was cancer, but it also noted other significant conditions that had contributed to his death were a history of cigarette smoking and coal mining. Conley’s wife filed for benefits under the Black Lung Benefits Act, which provides for victims of black lung disease caused by coal mining. To qualify for benefits under the act, the exposure to coal dust must be a substantially contributing factor leading to the person’s death, which, under the statute, means “hastens death.” The U.S. Department of Labor collected Conley’s work and medical records. An administrative law judge (ALJ) reviewed the record and took testimony from several physicians about the cause of Conley’s death. Only one physician testified that the coal dust was a substantial factor leading to Conley’s lung cancer, but he offered no evidence other than his testimony to support his conclusion. The ALJ nevertheless ruled that coal mining had hastened Conley’s death and awarded benefits to Mrs. Conley. Conley’s employer appealed to the Benefits Review Board (BRB) for black lung claims. The BRB reversed the ALJ, finding that there was insufficient evidence to hold that coal dust was a substantial factor that triggered Conley’s lung cancer. Mrs. Conley appealed to a federal appellate court. Should the federal court defer to the ALJ’s decision on the cause of Conley’s death? Why or why not? Which decision does the federal appellate court review, the ALJ’s conclusions or the BRB’s reversal? [Conley v. National Mines Corp., 595 F.3d 297 (6th Cir. 2010)]