A Ravalli County jury found Anne Stout guilty Thursday afternoon of killing her husband, Bill, last June.
The verdict followed nearly three weeks of testimony.
Bill Stout was found dead at his Darby-area home with a bullet wound in his head last June. His wife, Anne, was charged with deliberate homicide.
Prosecutors said Anne Stout plotted to kill her husband after discovering he had been involved in an extra-marital affair.
"One year and eight days ago, Bill Stout had no idea it was his last day of life," Ravalli County Deputy Attorney Bill Fulbright told the jury Wednesday. "This was a devious crime, but not meticulous. In fact, it was done sloppy. The defendant left behind trails of physical evidence that triangulate all around Anne Stout."
Stout's attorney, Ed Sheehy, attempted to convince the jury Stout's death was a suicide.