Called “touch” testing, it's a fairly new forensic technique requiring a small sample of cells that could be deposited on something like an article of clothing, Gibson said.
The police captain said investigators are looking for evidence of a second perpetrator or corroborating the DNA evidence under Marie Williams' fingernails.
“But DNA testing is only as good as our ability to match it to somebody,” he said. “Say the killer has since died, maybe got hit by a car, then we'll never be able to get a match. They will have carried their DNA to the grave.”
Detectives follow up on every tip, some of which trickle in periodically, Gibson said.
Most recently, detectives entered investigative reports on Nov. 9 and Dec. 3 of this year, based on interviews they conducted after receiving tips.
“Nothing substantive came out of the interviews, but it shows that the case is still active. We continue to get tips that we pursue,” Gibson said.
The bodies were discovered Dec. 6, 2003, after a landlord became worried because she hadn't received a rent check.
Nothing appeared to be taken from the house, Gibson said, but John Patrick Williams' brown Mercedes-Benz was found parked about a block away on Jenkins Avenue, near the railroad tracks.
“Not his normal parking place,” Gibson said.
The keys to the car have never been found.
John Patrick Williams had a tight circle of friends, who have tried to help investigators develop leads, the police captain said.
“We encourage them to reach out to us, to rethink the case. We believe they still might know something that could help us,” Gibson said.