MORGANTOWN, W.Va. -- Investigators, federal prosecutors and the trial judge acted properly in the case against a former Upper Big Branch mine official convicted of ordering a subordinate to destroy documents, and U.S. Attorney Booth Goodwin said the verdict should be upheld.The top prosecutor for West Virginia's Southern District filed his response to former security chief Hughie Elbert Stover's appeal on Thursday in the U.S. 4th Circuit Court of Appeals in Richmond, Va.In the 68-page brief, Goodwin said there's no merit to claims that U.S. District Judge Irene Berger erred in refusing to throw out Stover's interview with investigators, or that she erred in refusing to dismiss the charges and acquit him.Stover was convicted last fall of lying to investigators and ordering a subordinate to destroy documents following the worst U.S. coal mine disaster in four decades. The April 2010 explosion at Upper Big Branch killed 29 men.The mine was operated at the time by Massey Energy, which was later bought by Virginia-based Alpha Natural Resources. Alpha recently sealed the mine.Stover 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. His case is tentatively scheduled for oral argument in late September.Stover argued that he was convicted despite "a total lack of evidence" that he lied or intended to impede the investigation of the disaster.He argued that Berger wrongly allowed evidence the federal Mine Safety and Health Administration obtained through a subpoena that had been issued by state regulators. The appeal also claimed that the West Virginia Office of Miners Health, Safety and Training overstepped its authority in issuing that subpoena.The questioning of Stover also violated his constitutional rights to remain silent while in custody or have a lawyer present, his lawyer argued.Goodwin, however, said Stover came to the interview with an attorney and was not in custody when he knowingly lied to the investigators, who had properly issued the subpoena."No one present at the deposition had the power of arrest," Goodwin wrote. Those who took Stover's deposition also told him he could take breaks at any time, "and the deposition took place at the mine academy, not a police station."Witnesses testified last fall that Stover instructed mine guards to send out radio alerts whenever inspectors entered the property, which is illegal. Stover denied those claims during the interview.Goodwin said the jury had "overwhelming evidence" to support its verdict.Stover also argued that he was asked ambiguous questions, but Goodwin said the investigators' inquiries "were clear on their face, and were unmistakable given the context in which they were asked.""His only argument here is he ordered the destruction of the mine records without criminal intent," Goodwin wrote. "At trial, when confronted with the question of why he did it, his only explanation was that the act was 'stupid.'"Besides the circumstantial evidence, jurors also considered Stover's testimony.Stover "put his own credibility directly at issue," Goodwin argued. "The jury was entitled not to believe him."Defendant denied, more than once, that he acted with any criminal intent. Any rational trier of act could find these denials are simply not credible," he wrote. "His concocted excuses for his actions were considered by the jury in this case and would support a similar guilty verdict by any other rational jury."Only one other person has been criminally charged in the disaster so far.Former superintendent Gary May pleaded guilty to conspiracy to defraud the federal government for his actions at the mine. He's cooperating with federal prosecutors in a continuing investigation and will be sentenced in October.