STEVE INSKEEP, HOST:
The sheriff of Pima County, Arizona, has cleared the relatives of Nancy Guthrie as possible suspects in her disappearance. The mother of the "Today" show anchor Savannah Guthrie has now been missing for more than two weeks, and investigators are focused on DNA recovered from a glove that was found about two miles from Guthrie's home. If that DNA doesn't match anything in their criminal database, investigators could turn to a technique called genetic genealogy, which New Hampshire Public Radio reporter Jason Moon knows all about. His podcast, "Bear Brook," tells the story of one of the first cases ever to use this technique. Good morning.
JASON MOON, BYLINE: Good morning.
INSKEEP: How does genetic genealogy work?
MOON: Well, it's a little bit like traditional DNA sampling that's been used in law enforcement since the '90s. It helps to compare it to that. So if you think about the way that has traditionally worked, police would find a DNA sample at a crime scene and then compare it to a DNA sample in their own database. And it worked kind of like fingerprints. You know, they would look for an exact match in their database.
INSKEEP: Yeah.
MOON: And, obviously, that's a limitation, though. So if the sample's not in your database, that DNA sample from the crime scene might not help you so much. Genetic genealogy is different because you're not looking for an exact match per se, you're just looking for the family tree of the person you're looking for. And law enforcement - they're not using CODIS. They're using commercial DNA databases where people have voluntarily submitted their DNA...
INSKEEP: OK.
MOON: ...Often in hopes of discovering their relatives.
INSKEEP: Wow. OK. So CODIS, that's the criminal database we're talking about.
MOON: Yes.
INSKEEP: These voluntary DNA samples, these are services like Ancestry, 23andMe. They've been very popular over the years. Is that where they would get the DNA?
MOON: It's not those particular services, but it's the same concept, but they're the smaller databases. So the big ones - Ancestry and 23andMe - they actually don't allow law enforcement to use their genetic databases for these type of searches, but there are smaller DNA databases that do allow it. And the way it works is it's based on this concept that, you know, the closer a relative is to you in your family tree, the more DNA you share with them. So, you know, a parent shares 50% of their DNA with a child, 25% with a grandchild and so on.
So say investigators put a sample into a genetic genealogy database, they get a 3% match, that means they've found someone who's related to the person they're looking for - probably a second cousin, based on that level of shared DNA. Which might not sound like a lot, but in the world of genetic genealogy, anything closer than a fourth cousin is a pretty sure bet that you can eventually figure out the identity of the person from your original DNA sample.
INSKEEP: I'm realizing how this might work. You would narrow it down using the DNA from 300-and-some-million Americans to 54 people - to pick a number - that might be related in that way. And then you would use other information to figure out who might be a plausible suspect, who might have been in Arizona at the time, for example.
MOON: Exactly. Exactly. This was a technique that was pioneered by hobbyists and then started to catch on in law enforcement circles about 10 years ago. And since then, many, many cold cases have been solved using exactly what you just described. Most famously, the so-called Golden State Killer case in California and the Bear Brook case in New Hampshire that I covered.
At the same time, it's raised concerns about genetic privacy. You know, the - these searches can sometimes happen without police search warrants, and the people who uploaded their DNA might not have realized their genetic info was going to be used by law enforcement.
INSKEEP: Wow. Thanks very much for the insights. That gives us an idea of what might be happening inside the criminal investigation in the disappearance of Nancy Guthrie. New Hampshire Public Radio reporter Jason Moon. Really appreciate it.
MOON: My pleasure.
INSKEEP: He is with the "Bear Brook" podcast, as well as New Hampshire Public Radio.
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