Prosecutors said Brad Reay, 47, stabbed his wife to death last winter just days after she asked for a divorce.
He killed her in revenge for an affair with a co-worker and then tried without luck to frame her lover, then his daughter, the jury was told.
Reay will be sent to prison for life -- without the possibility of parole -- for the brutal stabbing death of Tami Reay, 41. The life sentence is mandatory in cases of first-degree for which prosecutors do not ask for the death penalty.
The daughter, Haylee, now 13, was in the courtroom with her mother's parents and one of her mother's sisters when the verdict was read. They sobbed openly and hugged prosecutors afterward.
Reay showed no emotion before he was led away in handcuffs.
The family will be allowed to be speak in court when Reay is sentenced. Circuit Judge Kathleen Trandahl denied a defense request to sentence Reay on Tuesday night and said she would decide Wednesday when to sentence him.
Tami Reay's nude body was found near Lake Oahe outside Pierre on Feb. 9. She had been stabbed dozens of times, and some of the wounds in her chest showed a knife had been forced in to the hilt. The weapon has not been found.
"She was blitz-attacked while she was asleep," Chief Deputy Attorney General Mark Barnett told the jury during closing arguments. "This is payback."
Brad Reay had acknowledged knowing that his wife had been dating a couple of men but said he did not know she was having an affair with a co-worker until after he was arrested.
He said that on Feb. 7, the night Tami was killed, he awoke to find his daughter standing over her mother in the woman's bedroom, "catatonic or in shock." His daughter had a knife in her hand, he said.
He said his daughter did not awaken from her catatonic state until after he had cleaned the blood off her, placed her in bed and asked her what she had done. Reay said that he and his wife had told their daughter a few days earlier about their plans to divorce and that she was upset with her mother.
Haylee testified last week that she never would have hurt her mother. The girl said she was afraid of her father and had never been very close to him.
