Woman Is Accused of Fatally Poisoning Boyfriend With Antifreeze for Inheritance

A North Dakota woman has been accused of fatally poisoning her boyfriend with antifreeze in what the authorities say may have been a plot to claim part of his $30 million inheritance.

The woman, Ina Thea Kenoyer, 47, of Minot, N.D., was charged with murder on Monday in the Sept. 5 death of Steven Edward Riley, Jr., 51, her boyfriend of 10 years.

Ms. Kenoyer was being held at the Ward County Detention Center in Minot, a city roughly 110 miles north of the state’s capital, Bismarck. She was set to appear in court on Wednesday; it was unclear if she had a lawyer.

On Sept. 4, emergency workers were called to the couple’s home in Minot, where Mr. Riley was found unresponsive, according to an affidavit prepared by Erin Bonney, an officer with the Minot Police Department, and filed in Ward County District Court on Monday.

Mr. Riley was taken to a local emergency room, and then transferred to a hospital in Bismarck, where he died on Sept. 5.

Ms. Kenoyer initially told authorities that her boyfriend had suffered a heat stroke, though an autopsy later revealed that Mr. Riley had died of poisoning from ethylene glycol, the main ingredient in antifreeze.

Mr. Riley’s friends and relatives said they believed Ms. Kenoyer had poisoned Mr. Riley with antifreeze, according to the affidavit, and told the authorities that she had made comments both before and after his death about poisoning him with the substance.

Investigators learned there had been discord in the couple’s relationship; Mr. Riley was set to receive a large inheritance, believed to be around $30 million, and had planned to leave Ms. Kenoyer once he claimed it.

Further flags were raised after one of Ms. Kenoyer’s friends reported seeing her dump Mr. Riley’s belongings outside their home on the day he became ill, according to the affidavit. The friend added that Ms. Kenoyer was upset because Mr. Riley was going to get his inheritance and leave her, it said.

Ms. Kenoyer told investigators after Mr. Riley’s death that she was entitled to part of the inheritance because she was his “common law” wife and that she planned to split the money with Mr. Riley’s son.

Some states recognize “common law” marriages, in which a longtime couple can be considered married without having gone through the formal legal marriage process. But North Dakota is not one of those states, and Ms. Kenoyer, according to the affidavit, was “incensed” when investigators explained so.

On Sept. 3, the evening before Mr. Riley was hospitalized, he had been at an airport to meet with a lawyer to finalize his receipt of the inheritance, according to the affidavit.

He was accompanied by Ms. Kenoyer and friends, who said Mr. Riley suddenly began to feel ill, complaining that he felt drunk despite not having consumed any alcohol.

He reported stomach pain and nearly collapsed, according to the affidavit.

“Witness stated they wanted to obtain medical treatment for John Doe, but Ina Thea Kenoyer was adamant that John Doe was suffering from heat stroke and just needed to go home and rest after the airport,” according to the affidavit, which identified Mr. Riley by the alias John Doe.

The next morning, a friend of Mr. Riley’s, Wesley Torgerson, dropped by the couple’s home to check on Mr. Riley’s condition. Ms. Kenoyer told him Mr. Riley was at a walk-in clinic.

“Torgerson went to every walk-in clinic in Minot as well as the ER and learned John Doe had not been to any of those locations,” the affidavit reads.

Ms. Kenoyer told investigators that Mr. Riley had been drinking alcohol all day on Sept. 3 and had suffered a heat stroke the day before, on Sept. 2, though a statement from a friend who had been with Mr. Riley on Sept. 2 contradicted her claim, and a toxicology report later revealed that Mr. Riley had no alcohol in his system when he died.

The authorities searched the couple’s home and discovered a Windex window cleaner bottle in the living room with green liquid believed to be antifreeze inside, court records show.

They also found a glass Coors Light beer bottle and a plastic mug, both suspected of containing antifreeze, in the garage, according to the affidavit.

Ms. Kenoyer suggested to investigators different scenarios in which her boyfriend could have accidentally ingested the antifreeze, including “smoking a cigarette that may have fallen into antifreeze in the garage.”

She also claimed that the symptoms of heat stroke “mimic poisoning,” according to the affidavit.

Ms. Kenoyer also acknowledged that she had served Mr. Riley sweet tea throughout the day on Sept. 3, according to the affidavit. Antifreeze is known to be easily disguised in sweet drinks, investigators said.

According to investigators, Mr. Riley was alone with Ms. Kenoyer at their home for at least 12 hours after the episode at the airport before she sought medical attention.

Ms. Kenoyer is the latest person to be accused of poisoning a romantic partner this year.

Last week, a Minnesota doctor was accused of fatally poisoning his wife, and in May, a Utah doctor who wrote a children’s book about grief was charged with killing her husband with fentanyl.