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 deliberation,” Judge Roger Klein told Shawna Nelson. “You deserve to serve every day of the sentence I will 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. She killed Heather Garraus, 37, on Jan. 23, 2007.

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.

Both Ignacio Garraus and Ken Nelson have resigned from their law enforcement jobs.