The woman who was having an affair with Patrick Frazee, a Colorado man accused of killing his fiancée, is expected back on the stand Thursday. Krystal Lee revealed new details Wednesday about the alleged crime, including Kelsey Berreth's apparent last words.

Berreth was last seen in public last Thanksgiving Day. Her body has not been found, but prosecutors allege Frazee killed her, reports CBS correspondent Nikki Battiste.

There were no cameras allowed in the Colorado courtroom Wednesday. CBS affiliate KKTV reporter Ashley Franco was in the court room as Lee, an Idaho nurse, took the stand.

"During most of her testimony she was holding back tears, she was letting tears go," Franco said. "It looked like she was giving herself time to get the answers out, but she was definitely struggling through it."
 
Lee was Frazee's secret girlfriend. She said Frazee asked her to kill Berreth, the mother of his child, three times, and when she didn't, he did.

Lee testified that Frazee told her he beat his fiancee to death with a baseball bat on Thanksgiving Day, and that Berreth's last words were, "please stop." After the murder, Lee said Frazee called her and said she had "a mess to clean up." 

"Krystal Lee says that when she walked into Kelsey Berreth's town home, she saw blood everywhere. … She was cleaning up this massive crime scene," Franco said.   

Lee claimed she drove from Idaho to Colorado and cleaned up the crime scene because Frazee told her to and she feared for her life. A few days after the murder, Lee said, she watched as Frazee burned a black tote bag that he told her contained Berreth's body and the baseball bat. 

More than 20 witnesses have been called to the stand so far. Earlier this week, a prosecution expert testified that a neighbor's surveillance camera captured Frazee 11 times at Berreth's condo the day she disappeared. The defense argued it's not clear if the person was Frazee. 

Franco said jurors have been paying close attention to everything. "Some of them had their heads down, taking notes ... You could see on their faces just the horror and the shock that they were in after hearing Krystal Lee's testimony," she said.

Frazee has entered a not guilty plea and faces life in prison if convicted. His defense team is expected to point the finger at Lee during the trial, pointing out she lied before about not knowing Frazee and Berreth.

In exchange for her testimony, Lee agreed to plead guilty to evidence tampering. She is expected to be back on the stand later Thursday morning.