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North Dakota woman arrested for allegedly killing boyfriend with poison; police cite "financial motives"

A woman in North Dakota was arrested and charged this week for allegedly killing her boyfriend, who died from poisoning last month, police said. They believe the suspect, identified as 47-year-old Ina Thea Kenoyer, may have had murdered Steven Edward Riley, Jr. for financial reasons. 

Kenoyer was taken into custody Monday and charged with class AA felony murder, the Minot Police Department said in a news release shared to its Facebook page. In North Dakota, a class AA felony could carry a maximum penalty of life in prison without the possibility of parole if there is a conviction.

Police charged Kenoyer in the death of Riley, a 51-year-old man from Minot, a city in North Dakota about 50 miles south of the Canadian border. Riley was in a relationship with Kenoyer, who is also from Minot, police said.

Riley died on Sept. 5 at a hospital in Bismarck after being transferred there from a local hospital in Minot. Results of a subsequent autopsy determined that Riley's official cause of death was poisoning with ethylene glycol — a key ingredient in antifreeze. Police believe that Kenoyer "had financial motives to murder Riley," they said. Kenoyer is being held at the Ward County Jail in Minot.

An affidavit supporting the warrant for Kenoyer's arrest, obtained Wednesday by CBS News, detailed the investigation that followed the death and preceded Kenoyer's detainment, including interviews with some of Riley's friends. 

Those friends told police that Riley "believed he was to become the recipient of a large inheritance and was planning on meeting a lawyer at the airport on 09/03/2023 to complete that transaction," according to the affidavit, which noted that Sept. 3 was the day Riley's friends reported witnessing his health "decline rapidly" at the airport. Earlier that afternoon, Theresa Akin — a friend of both Riley and Kenoyer — said she had seen Kenoyer throwing some of Riley's property outside. Akin told police that Kenoyer was angry because Riley "was going to get his inheritance and leave her." Kenoyer believed Riley was going to receive more than $30 million, the affidavit said.

Minot woman arrested for allegedly killing boyfriend with poison. The Minot Police Department arrested a Minot woman on...

Posted by Minot Police Department on Monday, October 30, 2023

On Sept. 3, friends told police that Kenoyer blamed Riley's increasingly serious symptoms on "heat stroke" and suggested that Riley "just needed to go home and rest after the airport." The friends also told police that Kenoyer "made comments after [Riley's] death that he was poisoned with antifreeze even though no lab work tests for antifreeze had been completed, and no medical professionals had conveyed any information about [Riley's] condition ... including the act that he died." 

A coroner later tested Riley's blood for ethylene glycol, a main ingredient in antifreeze, and found that he had toxic levels of the compound in his system when he died.  Kenoyer had previously suggested that Riley had been drinking a significant amount of alcohol, but tests administered when Riley first arrived at the hospital showed no signs of it in his body.

Kenoyer told detectives after Riley's death that she planned to split his inheritance with his son, since she considered herself to be his "common law wife" after a decade of dating. 

"Ina Thea Kenoyer was incensed when apprised by detectives that North Dakota does not recognize common law marriage and she would in fact not be entitled to a portion of any inheritance," the affidavit said. 

"This case was extremely complex," said Capt. Dale Plessas, the investigations commander at the Minot Police Department, in a statement. "Thank you to everyone who provided us with information that helped our investigators piece this together."

An investigation into Kenoyer and the circumstances leading up to Riley's death is still ongoing.

The alleged incident in North Dakota marked at least the fourth time this year that someone has been accused of using poison to kill their spouse or partner in the U.S. Just last week, a poison specialist and former medical resident at the Mayo Clinic in Minnesota was charged with fatally poisoning his wife, a 32-year-old pharmacist who died in August.

In May, the author of a children's book on grief was accused of killing her husband by poisoning him with a lethal dose of fentanyl at their home in Utah. And, in March, a Colorado dentist was arrested on suspicion of first-degree murder after police say he laced his wife's pre-workout shakes with arsenic and cyanide.

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