GREELEY, Colo. -- The prosecution's star witness in the Shawna Nelson murder trial pleaded guilty Friday morning to accessory to the crime of attempted murder in the first degree.

Michelle Moore testified last month against Nelson, her former best friend.

Nelson was convicted earlier this week of the Jan. 23, 2007, ambush slaying of Heather Garraus. Nelson had a near three-year affair with Garraus' husband, Ignacio, and gave birth to his child.

On the stand, Moore described how she suggested Nelson shoot Heather Garraus through a car window so it would act as a barrier to DNA evidence. Other suggestions included using a silencer and gloves.

Moore said Nelson told her she “could just walk up and shoot Heather in the head.”

During cross examination, Nelson's defense attorney suggested the two women were romantically involved, though Moore denied the relationship was sexual.

Nelson later contradicted her testimony and said that she and Moore had a sexual relationship.

Moore's testimony came as part of a plea bargain with prosecutors.

In return for her guilty plea to accessory and her promise to testify truthfully against Nelson, prosecutors dropped the more serious charges of conspiracy to commit and criminal attempt to commit first-degree murder.

Those charges could have carried a sentence of up to 48 years. Now, Moore could face up to nine years behind bars.

"It's clear that she's going to face the potential of a significant prison sentence," said defense attorney Andy Gavaldon. "So she didn't get away with anything. She's being held accountable, and she's accepting responsibility."

Moore, a former sheriff's deputy, is eligible for probation and intensive probation, but prosecutor Greg Lammons said, "I don't think those possibilities are strong, but that's ultimately up to the judge. I think it deserves a prison sentence and I think that's what will happen."

Moore will be sentenced on April 21.

Nelson was found guilty of first-degree murder and was sentenced to life without parole.

Read Lance Hernandez' Blogs:

• March 1, 2008: Shawna Nelson Trial Blog: Jury Recesses For Weekend
• February 27, 2008: Nelson Trial Blog Day 5: Forensic Experts Link Casings To Gun
• February 26, 2008: Blog Day 4: Husband, Best Friend Testify
• February 25, 2008: Blog Day 3: Nelson’s Interrogation Tape Shown
• February 22, 2008: Blog Day 2: Suspect’s Lover Testifies
• February 21, 2008: Blog Day 1: 911 Tapes Played