"At this stage, though," he said, "the value of the defendant's cooperation cannot be properly assessed" for such an argument.
So far, the investigation has led to two other criminal prosecutions.
Former security chief Hughie Elbert Stover is in prison in Kentucky, convicted of lying to investigators and ordering a subordinate to destroy documents during the investigation.
A former president of another Massey coal company, meanwhile, is also cooperating with prosecutors.
Former White Buck Coal Co. President David C. Hughart is set to enter a plea to two federal conspiracy charges Jan. 16, the day before May's sentencing.
Hughart is accused of working with unnamed co-conspirators to ensure miners at White Buck and other, unidentified Massey-owned operations, got advance warning about surprise federal inspections many times between 2000 and March 2010.
Prosecutors say that gave workers time to conceal life-threatening violations that could have led to citations and shutdowns.
Carrico said May acknowledges he should have disassociated himself from the policies and practices that Massey used to subvert inspectors and give miners underground advance warning of their arrival.
But he has otherwise led an "exemplary life" with "absolutely no criminal history," Carrico argued, and his 24-year career as a coal miner is effectively over.
He's now supporting his wife and two daughters as a truck driver, he said, and is not likely to engage in any criminal conduct in the future.