While pleading guilty to conspiracy himself in an ongoing investigation to the UBB tragedy, testimony by White Buck Coal Co. President David C. Hughart against Blankenship may pave the way for further indictments. Under questioning, however, he would only refer to Blankenship’s title, not name, in the Beckley, W.Va., courtroom. Though U.S. Attorney Booth Goodwin has declined to elaborate on how his strategy will proceed, other prosecutors have noted convicting a senior executive for safety violations in mining accidents can be difficult.

William Taylor, Blankenship’s attorney, for his part, dismissed Hughart’s testimony, given its context. “Don Blankenship did not conspire to do anything illegal or improper,” he said in an email to The Associated Press. “It is not surprising that people embellish or say untrue things when they are attempting to reduce a possible prison sentence.”

Hughart has been charged with working to provide miners at White Buck and other Massey subsidiaries advance warning about Mine Safety and Health Administration (MSHA) inspections between 2000 and March 2010. The 54-year-old is the highest-level Massey employee in the investigation. On sentencing in June, he faces up to six years in prison and a $350,000 fine for two counts of conspiracy. Massey was fined $10.8 million for violations stemming from the UBB explosion.

A superintendent, meanwhile, has already been given a 21-month sentence after pleading guilty to defrauding the government, while two other people have been convicted for their roles in the UBB incident.