The mother of a Utah grief author awaiting trial for allegedly poisoning her husband was also possibly involved in the man's death, a newly released court affidavit revealed. 

The Summit County Sheriff's investigator wrote in the affidavit it is "possible" that Lisa Darden, the mother of Kouri Richins, was "involved in planning and orchestrating" Eric Richins' death.

Investigators discovered Darden had been living with a female romantic partner who died suddenly in 2006. An autopsy determined the woman died of an overdose of oxycodone, the affidavit said. The woman struggled with drug abuse, but at the time of her death she wasn't in recovery, which the investigator said would "likely rule out the possibility of an accidental overdose." Darden had become the recipient of the partner's estate shortly before her death, the affidavit said.

The affidavit also said conversations "have been found on Kouri's phone showing disdain for Eric on Lisa's part."

"Based on Lisa Darden's proximity to her partner's suspicious overdose death, and her relationship with Kouri, it is possible she was involved in planning and orchestrating Eric's death," the affidavit states. 

No charges have been filed against Lisa Darden.

Eric Richins was found unresponsive in his bed after he, his wife and her mother had been celebrating after Kouri Richins closed on a real estate transaction for her business, investigators said.

Investigators determined Eric Richins died from fentanyl poisoning, with a medical examiner finding he had five times the lethal dosage of fentanyl in his system. The fentanyl was determined to be "illicit" and not pharmaceutical grade, the affidavit said.  

Eric Richins' family believes Kouri Richins spiked his drink the night he died, according to "48 Hours."

A year after her husband's death, Kouri Richins wrote a children's book on coping with grief, which she promoted on a local TV show caled "Good Things Utah." She was arrested a month later.

Darden previously spoke with "48 Hours" about her daughter's arrest, saying she was "shocked" when it happened.

She said her daughter and son-in-law had a great marriage, but one that was not without problems. The couple had three sons. Eric Richins owned a successful masonry business in Utah while Kouri Richins worked on her real estate business selling houses. But prosecutors say Kouri Richins began stealing funds from Eric Richins' account in 2019. Her family denies she ever stole from her husband.

In:
• Utah
• Crime