Hess was accused of leaving a Berkeley County bar with Grove, 46, early on the morning of Oct. 25, 1999, and driving her in his car to an orchard near Arden-Nolville Road.
Hess has said they went to the orchard for the purpose of having sex, and it was there that Grove was repeatedly beaten and stabbed.
Hess said in a confession to police that he attacked Grove because he felt guilty about committing adultery.
Defense attorney Craig Manford had maintained that a series of head injuries, especially one from a 1993 car accident that left Hess in a coma for days, combined with heavy drug and alcohol use before Grove died, meant Hess couldn't mentally form the intent to commit a premeditated act. Premeditation is a requirement for a first-degree murder conviction.
The jury thought otherwise.
"We considered all that, yes," said jury foreman Ronald Unger in an interview after court adjourned. "We went by all the evidence we had. Just because he was in an automobile accident in 1993 and was in the hospital for three or four weeks - a lot of people are in car accidents."
Manford had argued that the best case the prosecution could make against Hess would be for second-degree murder, without premeditation. Jurors also could have rendered a verdict of first-degree murder with mercy, meaning Hess would have been eligible for parole after 15 years.
Unger said the brutality of the crime played a role in the jury's decision.
"We had quite a bit of discussion, 'did his mental capacity and alcohol and drug use excuse what he did?'" Unger said. "That wouldn't lead you to kill her like he killed her, over and over and over again."
"This is the verdict the family wanted," said Berkeley County Prosecuting Attorney Pamela Games-Neely. She had argued that Hess' mental condition was being used as an excuse for a horrible act of murder.
People close to Grove said the verdict was the best they could have hoped for in West Virginia, which does not have the death penalty.
"It's the best we could get," said Grove's son, Jason Stevens, 25. "We'll have to live with it. I wish West Virginia had the death penalty."
"If he appeals this, I hope it goes nowhere - it shouldn't," said Candy Saville, Stevens' fianc.
Family members said they don't believe Grove left the Fifty Yard Line Club early that morning to have sex with Hess, as he has claimed. She did not have a driver's license and always had someone give her a ride to her home, which was about a mile from the club, they said.
"Nobody will ever make me believe she went out to an orchard to have sex," said Kenny Stevens, Grove's ex-husband and the father of her two children. "If that's what she wanted to do, she would have gone home."
"This was in the paper eight times," said Hess' father, Jerry Lee Hess Sr. "There's no way that jury didn't read this and know about this. I ain't sold on that one."
This was the second murder trial in three months for some members of the family. Roger Linaburg, the husband of Hess' sister Deanna Linaburg, pleaded guilty to second-degree murder midway through a first-degree murder trial in November, 2000.