Blankenship has been re-emerging as a public figure over the past year, launching a website where he shares his thoughts and calls the day the mine near Montcoal exploded one of the worst of his life.
Those in West Virginia's coalfields hold Blankenship personally responsible, accusing him of putting profits before people throughout his long career as a union-busting operator.
Multiple investigations found the Upper Big Branch blast was caused by blatant disregard of federal safety laws, and Blankenship had a well-documented record of micromanaging his mines.
"If the investigation into the tragedy at the Upper Big Branch mine is to be complete, Don Blankenship's indictment — and then conviction — is the only possible outcome," United Mine Workers of America President Cecil Roberts said Thursday.
But when Hughart was charged last fall, several former federal prosecutors told the AP it won't be easy to prosecute Blankenship. Kendall Coffey, a former U.S. attorney in Miami, said prosecutions of financial fraud have been more successful, but in fatal safety cases it's sometimes difficult to prove a crime was committed.
"It's historically been difficult to move to the top of the pyramid. Typically a chairman or CEO has multiple layers and relatively few fingerprints on the operational issues that directly cause a tragedy," Coffey said.
To reach the top, experts say, investigators would most likely need documents or other hard evidence to match witnesses' damning testimony. Either that, or they'll need multiple witnesses.
At least one potentially powerful document has already been made public.
After a 2006 fire that killed two men at a different Massey operation, attorneys in a civil lawsuit found a memo from Blankenship. He told workers at the Aracoma Coal Alma No. 1 mine that if their bosses asked them to build roof supports or perform similar safety-related tasks, "ignore them and run coal."
"This memo is necessary only because we seem not to understand that the coal pays the bills," he wrote.
Massey settled that lawsuit for undisclosed terms, and its subsidiary paid $4.2 million in civil and criminal penalties.
Blankenship had long been a public figure and household name in West Virginia, lavishing millions on conservative political candidates including state Supreme Court Justice Brent Benjamin, and accusing the former head of the federal Mine Safety and Health Administration of lying to Congress.
But the disaster made him known outside the state, and a week before his retirement, a national magazine profile labeled him "the dark lord of coal country." Upper Big Branch has since been sealed by the company that bought out Massey, Virginia-based Alpha Natural Resources.
Neither Hughart nor attorney Michael Whitt commented after the hearing. But Hughart's son, Jonathan, said he wants to see Blankenship in court.
But "Don Blankenship is a very powerful person," he said. "He won't see a day in prison. I promise you that."
Smith contributed from Morgantown.