Claims Kelsey Berreth's fiance asked woman to help kill his wife

There are claims murder suspect Patrick Frazee asked an Idaho woman to "kill the mother of his child" a month before Kelsey Berreth, 29, vanished on Thanksgiving.

Joe and Patty Rockstahl told KMVT they contacted the FBI after they realised the information one of their employees told them was about the Berreth case.

The couple owns the Rockstahl Law Offices, according to Fox News. They allege one of their employees told them in October that her best friend said "a man had asked her to kill the mother of his child".

The friend, Krystal Lee, is being investigated in connected with the disappearance.

Berreth’s phone gave off signals from Idaho three days after she was last seen alive and while authorities believe she is dead, they are yet to find her body.

Joe Rockstahl told KMVT, "If we couldn've gotten the police to call or drive by and say, 'Are you thinking of killing someone?' that would've stopped it. We wouldn't be here. We wouldn't have all of this going on."

The Rockstahls say they requested a meeting with Lee but it didn't happen and the friend asked them to "forget the whole thing".

They say they didn't contact authorities sooner because they were concerned the information was vague and secondhand.

Patty Rockstahl said she phoned the FBI after seeing Cheryl Berreth's mother pleading for her daughter's return.

"I think the mother that had the courage to go on TV when her daughter was missing, saying that someone knew where she was at," Patty Rockstahl said. "At that point in my mind I thought that Patrick, and that was the only name I had heard him called, I didn't know his last name, had done something to her daughter and he knew where she was at."

The Colorado mother was last seen on a surveillance video entering a Safeway grocery store in Woodland with her 1-year-old daughter Kaylee, whom she shared with Frazee. 

Frazee was arrested in December and charged with first-degree murder, first degree felony murder and three counts of solicitation to commit first-degree murder.