RIGHT NOW: Witnesses in the Kouri Richins case have changed their testimony, and this could be how the case CHANGES…

The accusations against Kouri Richins already read like an Agatha Christie mystery novel: The Utah soccer mom of three is accused of killing her husband, Eric Richins, lacing his evening cocktail with five times the amount of lethal fentanyl in March 2022.

And now the woman who already wrote one book based on her life as a widow — a children’s book about a child dealing with the sudden death of his father — is writing another: a jailhouse mystery thriller taking place in Mexico, and which she is writing from her jail cell in Summit County, Utah, her brother, Ronney Darden, tells PEOPLE, saying the book is “loosely based on what’s going on, but definitely fiction.”

News of Kouri’s second book comes on the heels of a 6-page letter that prosecutors filed into evidence September 15, and which they allege in court documents she was “engaging in witness tampering,” directing her brother, Ronney, “to testify or inform falsely.”

The accusations against Kouri Richins already read like an Agatha Christie mystery novel: The Utah soccer mom of three is accused of killing her husband, Eric Richins, lacing his evening cocktail with five times the amount of lethal fentanyl in March 2022.

And now the woman who already wrote one book based on her life as a widow — a children’s book about a child dealing with the sudden death of his father — is writing another: a jailhouse mystery thriller taking place in Mexico, and which she is writing from her jail cell in Summit County, Utah, her brother, Ronney Darden, tells PEOPLE, saying the book is “loosely based on what’s going on, but definitely fiction.”

News of Kouri’s second book comes on the heels of a 6-page letter that prosecutors filed into evidence September 15, and which they allege in court documents she was “engaging in witness tampering,” directing her brother, Ronney, “to testify or inform falsely.”

Kouri’s defense lawyers said in a motion obtained by PEOPLE that the publication of the letter in the court record was a violation of the gag order placed on lawyers on both sides of the case, calling it “an extrajudicial statement made for the apparent purpose of influencing the court of public opinion.”

Kouri has begun prelaw studies since her May incarceration, and the letter — which has been obtained by PEOPLE — was folded into her “10 Actual, Official LSAT Preptests” book in her cell. It allegedly included a host of directions to her mother, Lisa Darden: reminding her to walk the dog, to send her Crest White Strips — and to instruct her brother, Ronney, to recall a very particular memory regarding her deceased husband’s alleged drug use, which is the crux of her defense.\

In the letter, Kouri allegedly reminds her brother – vis-à-vis the letter to her mother – of a conversation he had with her now-deceased husband in which Eric confides in him about his alleged fentanyl habit and says that he gets drugs from the family’s ranch hands. She allegedly further notes that Eric had instructed Ronney “not to tell me because I would get mad because I always said he just gets high every night and won’t help take care of the kids.”

Adding asterisks around the words, Kouri also allegedly told Lisa that Ronney could “reword this however he needs to, to make the point. Just include it all.”

Officer Jeremy Thomas, who recovered the letter from Kouri’s cell, wrote in the incident report obtained by PEOPLE that the letter “appeared to be strategically written to coordinate a defense,” noting that “Kouri gives her mother instructions to contact people involved in the case and what statements/ testimony to give.”

But now, in a jailhouse call between Kouri and her mother over the weekend and transcribed by prosecutors in court filings obtained by PEOPLE, Kouri claims the letter, addressed to her mother, wasn’t written to her mother at all but is rather an excerpt from what she calls “this fictional mystery book.”

“Those papers were not a letter to you guys, they were a part of a freaking book,” Kouri allegedly said in the September 16 phone call.

The book, as described by Kouri and her brother, Ronney, is a fictionalized account of her own life: She is still represented by lawyer Skye Lazaro, but at her June bail hearing, she’s actually let out of jail.

“I go to Mexico and I’m trying to find these drugs,” Kouri says to her mother on the call, describing what happens to her protagonist. She adds that the protagonist goes into a Mexican prison, where she drinks lots of coffee — thus the need for the Crest White Strips that are requested in the letter.

Kouri tells Lisa on the call: “You can tell the whole thing is very much a story.”

Fictitious mystery novel or not, the letter allegedly violated three jailhouse rules, according to the incident report, noting that Kouri was locked down “pending discipline and issued a violation.”

In text messages Kouri sent to a friend through an approved jailhouse messaging device and obtained by PEOPLE, she said that as a result of the letter, she was in lockdown for 30 days — allowed one hour a day outside her cell for showers and phone calls — and barred from having visitors for the same length of time.