Hughart is the third person to face serious criminal charges in connection with Upper Big Branch.
Former superintendent Gary May is also cooperating with prosecutors. He was scheduled to be sentenced Jan. 17, but last week, Goodwin filed a motion to delay that.
May continues to provide important cooperation in the criminal probe, Goodwin said, adding that notable progress has already been made. Delaying his sentencing "will allow that progress to be extended and will avoid any risk to the investigation from the sentencing proceeding itself," he said.
Former Massey security chief Hughie Elbert Stover, meanwhile, is appealing his conviction last fall on charges he lied to investigators and ordered a subordinate to destroy documents.
He was sentenced to three years behind bars — one of the stiffest punishments ever handed down in a mine safety case — but has been free pending appeal. Witnesses testified that Stover instructed mine guards to send radio alerts whenever inspectors entered the property.
He's denied any wrongdoing.