A woman who donned a black mask, ordered her ex-lover's wife to her knees and shot her twice in the head was convicted of murder and sentenced to life in prison without parole Monday.

"You carried out this plan with great planning and deliberation," Judge Roger Klein told Shawna Nelson. "You deserve to serve every day of the sentence I am about to impose."

Nelson showed little emotion as the verdict was read and declined the judge's invitation to make a statement before he handed down the sentence.

Jurors deliberated for six hours since Friday before convicting her of killing Heather Garraus, 37, on Jan. 23, 2007.

Shawna Nelson's attorneys said they would appeal her conviction.

Nelson, a Weld County sheriff's dispatcher at the time, had a long affair with Garraus' husband, Ignacio, who was a Greeley police officer.

They had a son together, but Ignacio Garraus broke off the relationship a month before the shooting.

Witnesses said the masked killer, dressed in black, confronted Garraus in the parking lot of the Greeley credit union where Garraus worked and told her, "You ruined my life. Get on the ground."

Garraus replied, "OK, OK," and knelt down, and the woman in black fired two shots from a gun and fled, the witnesses said.

Nelson contended she was on her way to a liquor store at the time.

The trial was moved to nearby Fort Collins in Larimer County because of pretrial publicity and the possibility that jurors might know the witnesses.

Nelson's husband, Ken Nelson, who was a Weld County sheriff's deputy at the time of the shooting, has been charged with evidence tampering for allegedly handling the gun that police believe was used to kill Heather Garraus.

Ken Nelson said during the trial that his wife knew how to shoot and load the weapon. He took the stand after the judge assured him his testimony would not be used against him in the tampering case.

Ken Nelson testified he was going to divorce his wife after learning she was having an affair with Ignacio Garraus and was pregnant with his child, but he said they reconciled and he agreed to help raise the child.

Ken Nelson had resigned from the sheriff's department before his arrest. Ignacio Garraus resigned from the police force a few weeks after his wife was killed.

Shawna Nelson's one-time best friend, Michelle Moore, pleaded guilty last week to being an accessory to crime after prosecutors accused her of helping plan the slaying.

Moore testified during Nelson's trial that she and Nelson had discussed how to kill Heather Garraus.

The defense tried to discredit Moore by portraying her as Shawna Nelson's lover. Shawna Nelson testified she and Moore had a romantic relationship, but Moore denied it.