SAN DIEGO, California (CNN) — Jury selection began Friday in the murder trial of David Westerfield, charged with murder in the death of a 7-year-old girl who was abducted from her home in February.

Potential jurors started the selection process by filling out questionnaires.

Westerfield, 50, is charged with kidnapping and murder Danielle van Dam, whose body was found along a rural road east of San Diego three weeks after she disappeared. He has pleaded not guilty to the charges. Prosecutors announced last month they will seek the death penalty.

Opening statements are not expected for another two weeks. Sources close to trial estimate it will last 12 weeks.

Danielle's disappearance drew national headlines and rallied scores of volunteers to search for her in the hills surrounding the family's suburban San Diego home. The girl's body was found in an isolated desert area 25 miles from the home.

Westerfield, a twice-divorced father of grown children, was arrested February 22. He first became a suspect in the disappearance because he had left on a desert camping trip within hours of Danielle's disappearance.

Judge William Mudd is presiding at the trial.

The murder charge against Westerfield is unusual since the victim still has not been found.

He was arrested after searches of his home and two seized vehicles turned up DNA matches with the victim's blood. Police also said they found other "DNA evidence" on an article of Danielle's clothing in her bedroom.

Danielle van Dam has been missing since February 1.

In addition to the murder and kidnapping, Westerfield is charged with possession of material depicting children engaged in sexual conduct and using that material for "personally engaging in and simulating sexual conduct."

According to police, the missing girl's only reported contact with Westerfield was when she sold Girl Scout cookies to him earlier this year. She was last seen February 1, when her father, Damon van Dam, put her to bed at about 10 p.m.

That night, Danielle's mother, Brenda, did not get home from an evening out with friends until 2 a.m. Danielle was not discovered missing until 9 a.m. on February 2.

Law enforcement officials and hundreds of volunteers searched for Danielle without finding her. District Attorney Paul Pfingst said Monday he was forced to conclude Danielle had been killed.