A judge on Friday formally sentenced to death the man who kidnapped, sexually assaulted and murdered 5-year-old Samantha Runnion (search) in 2002 — a case that led to the expansion of child abduction alerts on electronic billboards along California's freeways.

A jury convicted former factory worker Alejandro Avila (search), 30, in April and voted for the death penalty in May. On Friday, Superior Court Judge William R. Froeberg endorsed the jury's recommendation.

"You shall suffer the death penalty," the judge told Avila, who looked away.

Avila snatched a kicking and screaming Runnion as she played outside her Stanton (search) home. Her nude body was found the following day in the mountains about 50 miles away, left on the ground as if it had been posed.

Authorities said she had been suffocated by pressing on her chest.

More than 4,000 people attended her funeral and then-Gov. Gray Davis ordered a statewide increase in the number of electronic billboards that flash information about a suspected abduction soon after it's reported.

A friend of Samantha's gave police a description of her kidnapper that produced a police sketch resembling Avila. Prosecutors used cell phone and bank records to show that Avila had been near where Samantha was abducted.

They also said Avila's DNA was under her fingernails, and sneaker prints and tire tracks found near the girl's body came from him. Samantha's DNA also was found on the inside of the door of Avila's car, probably from tears or mucus, prosecutors said.

The defense challenged the reliability of the DNA analysis and suggested that the material found inside Avila's car had been planted.

After the conviction, defense attorneys urged jurors to spare Avila's life, arguing that the abduction was an impulsive act prompted by a brutal childhood in which he was beaten by his father, raped by an uncle and neglected by his mother.

Samantha's killing was one in a series of child abductions, including 7-year-old Danielle van Dam of San Diego and 15-year-old Elizabeth Smart in Utah.