For over three decades the disappearance and vicious murder of Michella Welch had left police at a loss. The 12-year-old had disappeared in March 1986 from a park in the city of Tacoma, in Washington State.
At the time, she had been babysitting her two younger sisters in Puget Park and had rode off on her bike to pick up some sandwiches.
When she returned her sisters were in a nearby business using the lavatory, and Michella is believed to have gone looking for them.
When Michella’s sisters returned they found her bike and the sandwiches by a table in the park, but their sister was gone.
A police dog discovered her body later that evening down a ravine. She had been raped and murdered.
At the time DNA was taken from the scene and placed into evidence, yet the investigation struggled and was eventually filed as an unresolved cold case.
However advances in DNA technology over the following decades prompted detectives to take another look at the case.
In 2006 police scientists managed to reconstruct a DNA imprint from items collected at the crime scene, although no link was found to any known offender in the United States.
Twelve years later progress came due to the growth of genetic genealogy, with its vast databases and archives, including from people researching their family history using DNA testing kits from companies like 23andMe and Ancestry.com.
“Genetic genealogy uses DNA technology to identify subjects by matching the unknown profile to a family member,” Tacoma Police Chief Don Ramsdell told reporters.
“Traditional genealogy is then used to build a family tree from publicly available websites,” he said.
The technology led police to two brothers, whose age and place of residence in 1986 eventually made them suspects. They were placed under surveillance as police waited for a chance to verify their genetic profiles.
Earlier this month one of them, Gary Hartman, ate breakfast at a restaurant with a co-worker, oblivious to the undercover investigator sitting at a neighboring table.
When Hartman left the investigator collected the napkin he used to wipe his mouth and sent it to a lab for analysis. The tests discovered that the DNA matched that found on Michella Welch’s body.
Police arrested Hartman without incident at a set of traffic lights and on Friday prosecutors charged the 66-year-old with first-degree murder and first-degree rape.
He is currently being held in custody in lieu of $5 million (£3.7 million) bail and is due to appear back in court on Monday.
“This case does truly represent the crossroads of good old-fashioned police work combined with improvements in technology,” Ramsdell said.
Pierce County prosecutor Mark Lindquist had a warning to criminals.
“Today we are at a point where, if you are a criminal and you left your DNA at the scene, you might as well turn yourself in now. We will catch you,” he said.