In July 2002, Samantha was snatched from her yard as she was playing with friends.
"Please, please let her go. She's such a sweet child," her mother, Erin Runnion, sobbed at the time.
A day later, reports The Early Show national correspondent Hattie Kauffman, Samantha's body was found alongside a mountain road, by a driver who made a frantic 911 call: "Oh my God, we found a dead body. Please hurry. I'm so scared. It's a little kid!"
"Calm down," the operator pleaded.
The nude body was displayed in such a way that it inspired fear the killer could strike again.
A police officer said, "How it was left was also like a calling card, like a challenge: 'I'm here, and I'm coming back.' "
One of Samantha's playmates described the kidnapper to a police sketch artist. When the drawing was released to the public, several calls came in, identifying the man as Alejandro Avila, who was then arrested.
In opening statements Monday in Avila's trial, prosecutors said DNA from Samantha's tear drops were found inside Avila's car.
"I said it was consistent with tears, we don't know for sure it was tears, but that evidence was found in the defendant's car," pointed out Assistant District Attorney David Brent.
Prosecutors believe Avila killed Samantha, after molesting her, so she could never be a witness against him.
He'd faced young witnesses before. In an earlier case, Avila was acquitted of molesting two girls. In that case, the jury believed him rather than the children.
"I blame every juror who let him go, every juror who sat on that trial and believed this man over those little girls," Erin Runnion said on "Larry King Live."
Erin Runnion told Kauffman last fall that she plans to attend Avila's trial every day: "I want to know every detail."
"Even though some things might be horrible to see?" Kauffman asked.
"Yes," Runnion replied. "The whole thing is horrible. As much pain as I might feel, it is nothing compared to what she went through. She can't fight anymore; I can fight."
What does Runnion want the world to remember about Samantha?
"That she was kind, loving, everything a child should be -- happy," Runnion says.
One of the first witnesses on the stand Monday was the playmate who saw Samantha abducted.
Clutching a stuffed animal, the 9-year-old told the jury Avila asked her and Samantha for help in finding a lost puppy, then grabbed Samantha and pulled her into his car.
"The evidence shows Samantha was taken kicking and screaming," Brent says, "and at some point, he gave her a blow to the head. …This case is really about the horrific murder of a 5-year-old child."
If convicted, Avila could face the death penalty.