A Lehi man admitted in court Thursday that he caused his wife's death by injecting her with heroin and then started their house on fire with the body still inside.

Edward R. Arnold, 46, pleaded guilty in 4th District Court to manslaughter, a second-degree felony, and three other felony counts in connection with the August death of his wife, Gaylene Arnold, 35.Following the plea, Judge Anthony W. Schofield sentenced Arnold to one to 15 years at the Utah State Prison.

"He admitted that he killed her, and that's what is important," said Sherilyn Aplanalp, Gaylene Arnold's sister. "If he really loved her, why did he try to get her to use drugs again?"

Edward and Gaylene Arnold separated last year after being married about five years. Their Lehi home was in foreclosure when the pair broke in and secretly stayed there for a few days last summer. While living in the empty home on Aug. 2, Arnold injected himself and his wife with heroin.

"(Gaylene) subsequently went into distress as a result of the heroin and he did not call anyone for help," Deputy Utah County Attorney Sherry Ragan told Schofield.

"He made efforts to conceal the body by putting blankets over it and putting notes on the door saying that they did not want to be disturbed," Ragan said.

Arnold even lied to Lehi police because he failed to tell them his wife's body was inside when they came to the northeast Lehi house and questioned him about a trespassing complaint.

Sometime between Aug. 2 and Aug. 5, Ragan said, Arnold hid the syringe that he used to inject the heroin. On Aug. 5, he filled the home at 2967 N. 600 East with natural gas and started a fire. When Lehi firefighters responded, they found Edward Arnold in the backyard. He told them his wife had been unable to escape the fire.

Arnold said little during Thursday's hearing other than answering Schofield's questions and pleading guilty. But his attorney said Arnold wants to apologize to his deceased wife's family.

"He loves his wife very dearly," said public defense attorney Randy Spencer. "Not a day or an hour or a minute goes by that he doesn't think of his wife."

But Gaylene Arnold's family said she would have been much better off without Edward Arnold. Although she had prior drug convictions, Gaylene Arnold was in therapy and was doing very well just before her death, they said.

"She was clean and she was trying to make a new life for herself and her son," said Velma Aplanalp, Gaylene Arnold's mother. "He kept harassing her and tried to get her to go back."

Gaylene Arnold's son from an earlier marriage moved to Colorado to live with relatives after his mother's death. He is now 13.

"This is obviously a very tragic situation," Spencer said. "Mr. Arnold realizes he owes a debt to society and he is prepared to accept the sentence in this matter."

In addition to manslaughter, Arnold pleaded guilty to arson, a second-degree felony; evidence tampering, a second-degree felony; and abuse or desecration of a dead human body, a third-degree felony. Schofield sentenced him to one to 15 years on each of the second-degree felony counts and one term of zero to 5 years on the third-degree felony. All four terms will run concurrently, Schofield said.