JEFFERSON COUNTY, Colo. - DNA results are being questioned in the Jessica Ridgeway kidnapping and murder case.
In court Friday, the lead defense attorney for suspect Austin Sigg called into question the quality of work done on the DNA evidence in the Ridgeway case and the attempted abduction of a jogger at Ketner Lake.
The defense team said it has received three memos from authorities that show three DNA samples may have been contaminated -- two in the Ridgeway case, one in the Ketner Lake case.
The Colorado Bureau of Investigation report on the Ketner Lake case said the Ketner Lake sample was in a tray of other samples. CBI officials said some of the other samples were contaminated but the jogger sample wasn't.
Contamination can occur when a DNA sample is heated. Sometimes gas or liquid from one sample may contaminate another sample.
In the Ridgeway case, no details were released about the possible contamination, but officials said those samples were tested individually.
Sigg pleaded not guilty last month to 18 counts in the Ridgeway and Ketner Lake cases, despite confessing to both crimes to 911 dispatchers.
A two-and-a-half week jury trial for the case is scheduled to begin Sept. 20.
While Sigg entered a plea of not guilty, his attorneys mentioned Sigg's mental health, indicating a plea of not guilty by reason of insanity was still on the table.
If convicted, Sigg faces life in prison with the possibility of parole after 40 years. Sigg, who is 18, cannot face the death penalty because he was 17 at the time of the slaying.
-- We caution readers that this story below contains gruesome details.
Jessica Ridgeway, 10, was abducted as she walked to school on Oct. 5, triggering a massive search that ended with the discovery of her dismembered body five days later in an Arvada open space field.
Jessica's remains were found when two men collecting litter in that field came across a shiny black plastic bag, said lead Westminster Police Detective Luis Lopez.
The men called their supervisor and the trio open the inner bag and found the girl's torso, which was missing her arms, legs and head, Lopez said. The rest of the girl's remains were found in the crawl space of Sigg's home, the detective said.
An autopsy showed Jessica died from asphyxiation due to strangulation or suffocation, Lopez said.
Sigg came onto investigators' radar on Oct. 19, when a neighbor woman called a tip line in response to police saying they had recovered a small wooden cross that might have been worn by the killer.
The neighbor said she knew a teen named Austin Sigg who had worn a similar cross, according to Lopez.
The woman said she was concerned about Sigg because he had dropped out of high school and "he was obsessed with death and the decomposition of bodies," the detective recalled.
Based on that tip, the FBI took a DNA sample from Sigg that day, Lopez said.
Four days later, Sigg called 911 and confessed, police said.
"I murdered Jessica Ridgeway, I have proof that I did," Sigg is heard saying on the recording. "I'm giving myself up completely, there will be no resistance whatsoever."
When the dispatcher asked Sigg if he had a criminal history, he confessed to a second crime.
"The only other (incident) was Ketner Lake, where a woman was attacked. That was me," Sigg said.
Lopez said Sigg's DNA was linked to "touch" DNA found on Jessica's torso, underwear, water bottle, boots and gloves as well as the clothing of the jogger who was grabbed at Ketner Lake.
During a search of Sigg's home, police seized computer equipment.
Westminster Police Detective Chris Pyler, who specializes in crimes against children, testified that child pornography images were recovered from a laptop and a computer tower seized at the home.
The Sigg family did not know the Ridgeway family, Lopez said. But it might have been a crime of opportunity.
In court, prosecutors presented a map showing the location of the jogger's attack, Ridgeway's home, and Sigg's home. All were within one mile of one another.
Sigg studied mortuary science at Arapahoe Community College and had interest in becoming a mortician.
-- Ketner Lake attack
About 1:15 p.m. on May 28, 2012, a 22-year-old woman was jogging when a man grabbed her from behind and tried put a chemical-laced rag over her mouth, police said.
The woman escaped and called 911, police said. Yet officers searching the area with a police dog were unable to find the attacker.