CONCORD, N.H. – If a man convicted of manslaughter and negligent homicide in the deadly 2010 explosion at his New Hampshire gunpowder plant is granted a new trial, a key prosecution witness will not be in the line-up.

David Oldham was the manager of the Black Mag gunpowder plant in Colebrook at the time of the blast. He was shot to death earlier this month during a home invasion in Columbia, New Hampshire.

Lawyers say the transcript of Oldham’s testimony in the 2013 trial of Craig Sanborn of Maidstone, Vermont, most likely could be read to jurors during a second trial, but the lead prosecutor in the case isn’t certain he’d pursue one.

State’s Attorney John McCormick said that was an “indispensable” witness.

McCormick called Oldham’s unsolved killing “disconcerting.”