FORT COLLINS, Colo. -- The prosecution's star witness in the Shawna Nelson love triangle murder trial was sentenced to nine years in prison for her role in the case.

Michelle Moore was Nelson's best friend 14 months ago. She knew about the plot to kill Heather Garraus but said nothing to police until after the murder. Moore was a Weld County deputy.

During Nelson's trial, Moore cooperated with prosecutors and testifed about Nelson's detailed plan to kill Garraus, who was married to Nelson's lover.

As part of a plea bargain, Moore pleaded guilty to being an accessory to the crime of attempted first-degree murder. She received the maximum sentence on Monday -- nine years in prison.

Moore had been released on bail and the weekend before she was to go to prison, Moore was out drinking, prosecutors said. She was arrested in Larimer County at 2:30 a.m. Saturday for suspected drunken driving.

"Moore did not complete roadside maneuvers consistent with sobriety," said Eloise Campanella, a spokeswoman for the Larimer County Sheriff's Office.

Nelson was convicted of first-degree murder in the Garraus slaying and is serving a life sentence.

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