pumps miners were supposed to wear to measure their intake of coal dust, but at upper big branch, bobbie pauleythey were routinely instructed by their bosses to cheat on the test, by hanging the pumps in the fresh air. >> pauley: so your measurements when they were tested came in compliant with the law. >> cooper: federal mine inspectors visited upper big branch almost daily but prosecutors say the mine had an illegal advance warning system in place. security guards at the entrance would relay messages to miners underground alerting them an inspector was coming. >> cooper: they would use code words? >> stewart: yeah, bad weather. >> cooper: they would say it's bad weather? >> stewart: uh-huh. which means, we'll let you know if he's coming your way or going some other way. >> cooper: so you would get word from up above that okay, an inspector's coming, they would use code words, and then you would basically clean up your area to make it look right? >> stewart: uh huh, yeah. >> cooper: upper big branch was a non-union mine. inspectors were the only people miners could turn to for help. but they s