FORT COLLINS, Colo. -- Heather Garraus was leaving work last year when someone in a black mask ordered her to her knees and shot her twice in the head.

On Tuesday, a woman who police say had been jilted by Garraus' husband goes on trial on a murder charge, accused of killing Garraus on Jan. 23, 2007.

Shawna Nelson, a former Weld County sheriff's dispatcher, faces life in prison without parole if she is convicted.

Nelson -- who was married -- had a longtime affair with Garraus' husband, former Greeley police officer Ignacio Garraus, according to court documents.

During jury selection Tuesday, two of the questions for potential jurors related to extramarital affairs. Specifically, jurors were asked, "What are your opinions of people who have extra-marital affairs?" and "Do you have any religious or moral beliefs or values that would affect your ability to be a a fair juror if a defendant or witnesses have extra-marital affairs?"

The affair that Nelson had with Ignacio Garraus produced a son, but he ended the relationship in December 2006, according to arrest warrant affidavits.

Nelson has denied any involvement with the crime, the affidavits say.

According to court documents, Nelson wanted Ignacio Garraus to leave his wife so the two of them could live with their son as a family. Nelson's husband, Ken Nelson, told investigators that Ignacio Garraus was "reluctant to accept custody of the child."

Five weeks before the murder, Shawna Nelson sent Ignacio Garraus a text message warning him to "Be prepared," according to information presented at a pretrial hearing.

"My loyalty is gone," the Dec. 18, 2006, message read. "I loved u and trusted you and u (expletive) me."

Ken Nelson, 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.

Investigators suspect Ken Nelson took the gun after stopping his wife's pickup and talking to her shortly after the slaying. They say he later turned it in.

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 best friend, a former Weld County deputy, is also accused of conspiracy to commit murder. According to her arrest affidavit, she knew of Shawna Nelson's plan to kill her rival but did not notify authorities.

On Tuesday, 132 potential jurors showed up in the Larimer County courtroom and were broken into three groups of 40-50 people. Individual questioning took place behind closed doors and is expected to continue through Wednesday.

One group is due back at 8 a.m. and another group will come back at 1:15 p.m.

Jurors were handed a combined list of potential witnesses from both the defense and prosecution and asked if they knew anybody on that list personally or socially.

Of the 300 names on the list, at least five names are law enforcement witnesses.

The shooting took place in Greeley, but the venue was moved outside of Weld County because a Greeley police officer, two Weld County deputies, and a Weld County dispatcher are involved in the case.

Also, someone in the Weld County District Attorney's Office had a relationship with Ken Nelson, 7NEWS reported.

Chief Judge Roger Klein from Greeley is hearing the case in Larimer County but he brought his entire staff, including a court reporter, with him. A juror made of Larimer County residents will hear the case and the Larimer County District Attorney's Office is trying the case.

Klein said opening statements won't start until Thursday. The trial is expected to last two weeks.