A Utah mom of three and children's book author accused of poisoning her husband to death last year allegedly asked her brother to falsely testify in a letter she wrote from jail, according to prosecutors.

Summit County Sheriff's Office deputies located the six-page, handwritten letter written to Kouri Richins' mother, Lisa Darden, in her jail cell while conducting a search, according to court documents.

In the letter, Richins writes that her attorney, Skye Lazaro, "wants to link getting drugs and pills from Mexico, so we need some kind of connection."

Richins, 33, allegedly killed her husband, 39-year-old Eric Richins, with a fentanyl-laced cocktail the evening of March 3, 2022, at their home in Kamas, just outside of Park City, while their three young sons were sleeping. Prosecutors allege Eric's murder was motivated by money.

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The letter further instructs Kouri's brother, Ronald "Ronney" Darden, to testify about Eric's "Mexico trips" to buy "pain pills and fentanyl."

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"Reword this however he needs to, to make the point[.] Just include it all," the letter reads. "The connection has to be made with Mexico and drugs. … Upon information and belief LOL."

Kouri-Richins

Kouri Richins, left, a Utah mother of three who authorities say fatally poisoned her husband, Eric Richins, then wrote a children's book about grieving, stands with her attorney Skye Lazaro during a status hearing Friday, Sept. 1, 2023, in Park City, Utah. (AP Photo/Rick Bowmer, Pool)

In a Sept. 15 filing, prosecutors said "no such link exists" between Eric Richins, Mexico and the fentanyl that led to his death. 

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"[T]he defendant concocts a false narrative for Ronald Darden to repeat," prosecutors said in their filing, adding that the letter shows "evidence of witness tampering. It is unclear if the letter ever made it to Lisa and Rodney Darden, according to the court filing.

Kouri apparently purchased four different life insurance policies on Eric's life totaling more than $1.9 million between 2015 and 2017. On Jan. 1, 2022, months before his murder, Kouri "surreptitiously and without authorization changed the beneficiary for Eric's $2 million life insurance policy to herself," a court document states.

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Prior to his death, Eric removed Kouri from his will and made his sister the beneficiary instead, according to investigators. 

A split image of Kouri Richins crying in court and her husband Eric Richins fishing

Kouri Richins, a Utah mom of three, is accused of killing her husband of nine years, Eric Richins, with fentanyl last year. (AP Photo/Rick Bowmer/ family handout)

Eric's family told authorities he had been in fear for his life after Kouri allegedly tried to poison him once several years ago in Greece and again on Valentine's Day 2022, when he says she tried to poison his sandwich.

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The couple was apparently having financial disagreements due to Kouri's wish to purchase a $2 million mansion under construction in Wasatch County. She wanted to flip the mansion and sell it for a profit, a warrant states, while Eric thought the project would be too expensive.

Kouri and Eric Richins and a mansion

Utah children's book author Kouri Richins had a contentious relationship wrought with financial disagreements with her husband before she allegedly killed him with fentanyl. (TownLift, Will Scadden/Facebook)

In another section of the letter, Kouri asks her mother to help spread the narrative that Eric Richins' sisters were "jealous" of her because "anything they could do, Kouri could do better."

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"Being a mom, college, stay at home wife [sic] until she built a million dollar company. A nice house, car, everything she had, they wanted," she wrote.

Kouri and Eric Richins smile together

An obituary for Eric Richins describes him as an "avid outdoorsman and dedicated hunter." He enjoyed helping his family's cattle ranch and growing his "successful" masonry business. The obituary also describes him as a dedicated family man. (Facebook/Kouri Richins)

A day after finding Eric dead in their bed, Kouri allegedly closed a deal on the Wasatch County mansion "alone."

Kouri told investigators the morning of March 4, 2022, she did not know what happened to her husband after calling police to report his death, calling the incident "insane," according to a transcript from police-worn body camera footage taken at the scene of Eric's alleged murder.

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After Eric's death, Kouri wrote a children's book about death, "Are You With Me?"

A description for the book, which was listed on Amazon for $14.99, describes "Are You With Me?" as "a must-read for any child who has experienced the pain of loss, and for parents who want to provide their children with the emotional support they need to heal and grow."