(CNN) As he waited for his murder trial to begin, Patrick Frazee sent letters to a man he met in jail asking him to kill some of the witnesses, the former inmate testified.

Frazee is charged with murdering Kelsey Berreth , the mother of his toddler daughter. She went missing last Thanksgiving Day and her body hasn't been found.

Frazee had asked more than once, the former inmate testified last week, according to CNN affiliate KMGH . The former inmate, who prosecutors asked the media not to identify, is now on probation, the station reported.

In handwritten letters, the prosecution said Frazee referenced "instruction or suggestions to carry out the hits so to speak on the witness" and named several potential victims, KMGH reported

One of the witnesses mentioned was Krystal Lee Kenney, who used to date Frazee and testified during the first week of trial that he made her clean up a bloody mess. She had also told the court he admitted to killing Berreth with a bat, according to KMGH.

The 33-year-old Colorado man is facing eight charges: two counts of first-degree murder, three counts of solicitation to commit murder, two counts of a crime of violence and one count of tampering with a body. He pleaded not guilty in May.

No cameras are allowed inside Frazee's trial. CNN has pieced together this wrapup of the second week of Frazee's trial based on KMGH's daily coverage.

Before court ended for the week, the judge said the jury will also be able to consider charges of second-degree murder and manslaughter.

During cross-examination, the former inmate testified he had previously considered selling Frazee's letters online. He told Frazee's attorney, Adam Stiegerwald, he hoped to get a plea bargain by testifying.

Colorado Bureau of Investigation (CBI) agent Gregg Slater testified the letters appeared to match Frazee's handwriting.

Frazee allegedly wrote in a letter Slater read out loud that he would "really like to see Kenney with a bullet in her head."

"I know the DA helped put words in her mouth. No video, no weapon, no body, no forensics ... They're coaching her on the circumstantial evidence for a blank statement to match up," one of the letters read.

Kenney, who initially lied to FBI agents about her involvement, later pleaded guilty to a lesser charge of tampering with evidence and agreed to testify against Frazee. The defense team has questioned the plea deal.

Without her testimony, Slater told the court last week, he didn't know where the investigation would be.

"We didn't know anything other than Berreth was missing, her belongings were missing ... her behavior was off," he told the court.

'People aren't easy to kill'

Investigators never found evidence to suggest Berreth was still alive, former Woodland Park Police Department Commander Christopher Adams testified during the second week.

They were also able to trace her gun, which Berreth had with her before she went missing, he testified. A special agent previously testified Kenney had taken Berreth's gun -- allegedly at Frazee's request -- back to her hometown in Idaho and then gave it to an old friend.

Adams said investigators collected it from that friend and later determined it had been purchased by Berreth in 2014.

That matched what Kenney had told the court. She had testified Frazee killed Berreth with a baseball bat in her townhome and then burned her body in a black tote on a ranch.

Caitlin Rogers, a CBI forensic analyst, also told the court blood samples collected from across Berreth's townhome matched her DNA.

A former police officer who now specializes in blood pattern analysis testified the blood patterns found in Berreth's home were consistent with someone being struck multiple times -- and with a bat.

"People aren't easy to kill," the former Denver officer, Jonathyn Priest, told the court. "They're very resilient. And beatings are nasty in that they don't really have the effect that they have on television."

He testified that bloody footprints found around Berreth's home indicated a "pool of blood" was stepped through.

"There is nothing here that tells me the death was accidental," Priest told the court . "It's very consistent with what I'd expect to see in a homicide."

When asked why more blood wasn't found, he told the court that Kenney's testimony of cleaning the crime scene would explain why a lot of the blood was gone.

Defense attorney Ashley Fridovich Porter confirmed with Priest he hadn't seen many of the blood stains before they had been cleaned and a big part of his analysis was based on Kenney's descriptions.

Tooth and phone fragments

Rogers, with the CBI, was also questioned about apparent tooth fragments authorities found in a burned area on a ranch. That's where Kenney testified Frazee burned Berreth's body in a black tote.

A DNA test from the tooth fragment detected female human DNA, the expert testified.

Adams County Fire Rescue Investigations Chief Jerry Means testified that photos of the burn area show there was melted black plastic -- consistent with how plastic of the black tote would have melted.

During her testimony, Kenney had also told the court that after the alleged killing, Frazee instructed her to take Berreth's phone and send texts to Berreth's mother and boss before taking the phone as far as she could.

Twin Falls, Idaho, police officer Josh Hayes testified last week that authorities found charred pieces resembling a phone in a burn pile about 500 feet away from Kenney's home.

A Teller County Department of Human Services employee testified that when she talked to Frazee after Berreth's disappearance , he told her they texted for two days after Thanksgiving.

Frazee said he spoke with Berreth again on the morning of November 25, Mary Longmire testified. He called her later that day and it went to voicemail, she testified that he told her.

The trial resumes Monday with closing arguments.