A judge will determine if there's enough evidence to continue the criminal case against Patrick Frazee in the death of his fiancé Kelsey Berreth following a preliminary hearing in Teller County Court Tuesday morning.

KUSA - Prosecutors are expected to lay out why they believe Patrick Frazee was responsible for his fiancé Kelsey Berreth’s death during a preliminary hearing slated for Tuesday morning in Teller County court.

> A camera will not be allowed in the courtroom during Tuesday's preliminary hearing. 9NEWS will have crews on the scene and provide updates to 9NEWS and 9NEWS.com as they become available.

Most documents in the case – which has generated national attention since Berreth’s disappearance in late November – have been sealed, though Frazee and his defense team have been given access to the evidence against him. Law enforcement investigating the case has been largely mum about what they believe motivated the crime.

“Preliminary hearings are designed to weed out a weak case,” 9NEWS legal expert Scott Robinson said. “So, the prosecution needs to put on evidence, but just enough to show there is probable cause for the charges.

“And for the defense, it’s an opportunity to find out everything they can about the prosecution’s case that might not have been revealed in the police reports, the discovery.”

Frazee was arrested on Dec. 22 – nearly one month after Berreth was last seen in surveillance footage at a Safeway in Woodland Park. He has since been charged with two counts of first-degree murder and three counts of solicitation to commit first-degree murder.

It's unclear if Krystal Kenney will testify at the preliminary hearing. Earlier this month, the 32-year-old Idaho nurse pleaded guilty to one count of tampering with physical evidence in regards to Berreth’s disappearance and said she will testify against Frazee.

In a statement, she said she had “learned Patrick Frazee had committed a homicide on approximately Nov. 22, 2018, in Teller County.” She admitted to moving Berreth’s cell phone with the “intent to impair the phone’s availability in the investigation.”

District Attorney Dan May said he could not comment on the current location of Berreth’s phone. Previously, police said that her phone pinged in Gooding, Idaho on Nov. 25. That same day, Berreth’s employer received a text from that number saying she wouldn’t be at her job as a flight instructor the ensuing week.

While investigators have said they believe she is not alive, Berreth’s body has not yet been found. Police believe she was killed in her own home, but they haven’t said why.

“At this point, authorities have not found the body of Kelsey Berreth,” Robinson said. “And that’s expected to be the only weakness in the prosecution’s case unless they can explain why the absence of a corpse doesn’t matter in the context of this case.”

Berreth’s mother first reported her daughter missing on Dec. 2 after saying she had a hard time getting ahold of her. On Dec. 12, she appeared at a news conference and pleaded for Berreth’s safe return. That same day, Frazee issued a statement through his attorney to reiterate that he had been cooperating with the investigation.

The next few days, law enforcement searched Frazee’s home but said they did not find Berreth’s body.

“The preliminary hearing will reveal for the first time three critical areas,” Robinson said. “No. 1: why are the police convinced that Kelsey Berreth is dead and that she was killed in her own home? No. 2: who did Patrick Frazee allegedly solicit to kill his fiancée and did that individual commit the actual homicide or was it Frazee himself?

“And finally, what connection – other than the disposal of the phone and the use of it to put authorities off from the scent – did the nurse from Idaho, Krystal Kenney – what was her role?”

Robinson also said the preliminary hearing could reveal how Kenney knew Frazee or Berreth.

According to a wrongful death lawsuit filed last week, Berreth’s parents allege that her disappearance stemmed from a custody battle with Frazee. In the lawsuit, they claim that the couple broke up on Thanksgiving and that Berreth agreed to share their 1-year-old daughter 50/50 – something Frazee, who sought full custody, did not want.

But, Robinson said the information contained in the complaint are merely allegations rather than information culled from the criminal investigation.

“It does not appear from the allegations in that complaint that the parents have more information about what the investigation can show than the general public,” Robinson said.

Since Frazee’s arrest, his child has remained in the custody of Berreth’s parents and child protective services. Multiple custody hearings have upheld this position.

Robinson said it’s hard to say if Frazee will take a plea deal like what happened in Colorado’s other recent high-profile murder case: the one against Chris Watts, who pleaded guilty to killing his pregnant wife and two young daughters to avoid the death penalty.

“What’s happening behind the scenes – we won’t know until it happens,” Robinson said.