TUCSON, AZ — DNA samples are not always the slam-dunk evidence you see on TV crime fiction.
Search crews looking for anything that might help find Nancy Guthrie found a black glove within two miles of her house. It looks like the gloves worn by a person seen on camera outside of Guthrie's home the night she disappeared.
However, DNA on a glove found about two miles from her house does not match anyone in the FBI database. It does not even match any other unidentified DNA collected at crime scenes over the years. The Pima County Sheriff’s Department says nothing on the glove matches any other DNA found at the house, but testing did show the glove holds the DNA of a man, and investigators are working to see if it could still help the case.
The fact that the profile does not match anyone in the FBI DNA database suggests it is not a match for anyone who has run through the US criminal justice system. Most of the profiles in the FBI DNA database are from people who have been arrested at one time.
But there’s another way DNA could help: services where people volunteer their DNA to learn their family history sometimes help solve a case.
Suzanne Carlstedt is a private investigator who knows how to make this work.
She says investigators can trace a path to relatives and use that to track down the suspect.
“Whether it be something that is contemporary or it is something that is, you know, decades old, you can start building out that family tree. And they can use, not only GEDMatch (a DNA genealogy site), but they get databases, but they can also use Ancestry.com or 23andMe to gather more and more information about who all is in that tree.”
Those connections can reveal the links to a life.
“I would be digging for, in this particular subject, do they have a relation to this area? Do they have a marriage license here? Do they own any property here? Does their phone tie back to here? What about their social security number? All kinds of things that databases, that private investigators can use, that would give information that normal people can't find, just Googling things.”
One example where this approach worked very well was in California’s Golden State Killer case. There, the DNA threads led to a former policeman who was a serial killer in the 1970s. In 2018, he pleaded guilty to 13 murders.
