5 chilling details about Merrilee Cox-Lafferty's murder 

On August 17, 2018, 37-year-old Californian Merrilee Cox-Lafferty, who battled severe epilepsy, drove to Cache County, Utah, with her 8-year-old daughter. Within 3 days, she had disappeared, and that trip became the last confirmed sighting of her alive. By August 21, she was a missing-person case.

Investigators spent 4 uneasy weeks piecing together CCTV clips, phone pings, and witness tips before finding her buried in a shallow grave off Left Hand Fork Canyon on September 14.

At 9 p.m. ET/PT on Tuesday, June 24, 2025, Investigation Discovery will debut See No Evil Season 14’s installment The Dog Knows, which puts this case in the spotlight. The broadcast revisits the entire timeline, from first alarm to courtroom reckoning, making it a timely refresher on a case that shocked two states.

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5 Key Details About Merrilee Cox-Lafferty’s Murder Explored

1) Coco the service dog cracked the case

Logan Police picked up Cox-Lafferty’s Australian-shepherd mix service dog, Coco, wandering the city streets on the day she was reported missing. Gary Jensen, Logan Police Chief, stated to the media, as per a Deseret News report dated September 15, 2018:

"The dog was pivotal. It offered us some information that we just simply didn’t have and may not have had had we not taken custody of this animal and ultimately release it to people that knew more about Merrilee and her circumstance."

Officers traced Coco back to longtime acquaintance Stacy Robert Willis in neighbouring Hyrum. This abruptly shifted the investigation from a missing person case to a homicide.

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2) A marijuana drop became a deadly rendezvous

Court filings show Merrilee Cox-Lafferty had agreed to deliver two large bags of marijuana to Willis. As per a Deseret News report dated January 23, 2019, prosecutors said the pair argued after she accidentally backed into Willis’s SUV.

He beat Merrilee Cox-Lafferty unconscious, loaded her into his pickup, and drove toward Blacksmith Fork Canyon as per a Deseret News report dated January 23, 2019.

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3) Digital breadcrumbs led to a canyon grave

Detectives “pinged” Merrilee Cox-Lafferty’s phone at 1:30 pm on August 18 near Blacksmith Fork Canyon. They pinged again 45 minutes later on U.S. 89/91. This helped build the probable-cause trail that allowed a full-scale search, as per a KSL report dated October 3, 2018.

Merrilee Cox-Lafferty's body was discovered 4 weeks later, buried in a shallow grave roughly eight miles off the paved roadway, confirming foul play.

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4) Willis lied to the victim’s child

Immediately after the killing of Merrilee Cox-Lafferty, Willis drove the 8-year-old to a relative’s home in Boise, Idaho. He allegedly told her that her mother had probably abandoned and left her.

As per a Deseret News report dated March 12, 2019, sentencing Judge Kevin Allen called that deception:

"That is incomprehensibly horrifying,"

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5) A judge’s scathing rebuke sealed a life term

Willis pleaded guilty, claiming to have "outburst disorder" to reduce murder charges on January 23, 2019, avoiding a possible death sentence. As per the Deseret News report dated March 12, 2019, at the March 11, 2019, hearing, Judge Allen delivered a withering assessment:

“You don’t have outburst disorder. You are just a mean, uncaring, self-absorbed horrible person,”

The judge handed Willis a 15-to-life sentence and advised that he spend the rest of his natural life behind bars. According to Utah Department of Corrections records, Willis will not see a parole board before the mid-2030s.

These 5 facts, Coco’s vital clue, the illicit drug hand-off, the digital trail, the cruel lie, and the courtroom reckoning, anchor the narrative viewers will watch unfold on See No Evil.

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Stay tuned for more updates.