SPOKANE, Wash. — For the first time, police have confirmed the role DNA played in identifying their suspect in the Moscow murder case, Bryan Kohberger.
In an 18-page affidavit of probable cause, investigators reported a knife sheath was found next to the body of Madison Mogen. On that sheath, Idaho's State Lab found a 'single source of male DNA,' which was labeled suspect profile. The sample was pulled from the button snap on the sheath.
"The reason DNA is so compelling is because it is a unique signature. Unless you have an identical twin, no one has your exact DNA," says CeCe Moore, Chief Genetic Genealogist for Parabon.
Moore pioneered the genetic techniques that have been used in solving hundreds of criminal cases, such as the Golden State Killer case in California (Parabon didn't work on that particular case).
The techniques can crack a case with only a tiny sample of DNA.
"Because technology has advanced so far, it is possible to just use a few skin cells in order to identify someone," Moore says. "That is true both for the traditional genetic forensic profile, that is what is court-admissible DNA evidence. It's also true for investigative genetic genealogy, we can work with the tiniest fragment of DNA, and that includes touch DNA. Based on the affidavit in this case, it looks like touch DNA is what they had to work with. That's just skin cells."
Moore says we are always shedding our DNA wherever we go, in our epithelial or skin cells, saliva, and even hair without a root. That's why, she says, with the advance of technology in genetics it's nearly impossible for criminals to go uncaptured.
"So, in this case, it looks like they had to take that tiny amount of DNA and perform two separate lab analyses on that, because the crime lab creates that STR profile, the one that is court admissible. But a private lab has to create the SNIP- based genetic profile that's used for genetic genealogy. And at this time, none of the crime labs have the capability to do that themselves. So it would have had to have been sent out. So clearly, even if it was a very small amount, there was enough to be able to do these two separate lab analyses, which is really interesting," Moore says.
Moore guesses, from her analysis of the affidavit, investigators zeroed in on Kohberger either because of a combination of the DNA evidence and technological evidence, like his type of car being seen near the King Road home numerous times, or that they "could have had good enough genetic genealogy matches that they were able to connect to both his mother's side of the family and his father's side of the family. And if they did that, it would have pointed right at him because he is the only son of that union."
Kohberger's affidavit shows three days before his arrest, December 27, Pennsylvania agents took trash from his parents home in Albrightsville. That's a common tactic for law enforcement to surreptitiously gather a suspect's or family member's DNA, Moore says.
"The Supreme Court, the federal Supreme Court has ruled when we throw something away, we are abandoning it. So we are abandoning our DNA everywhere we go. That has been ruled, at least so far, that's fair game for law enforcement."
That garbage was sent to the Idaho State Lab, and within a day the lab had another DNA profile.
"It certainly appears they recovered his father's DNA from the trash," Moore says. "They wouldn't have known which males' DNA that would've been until they looked at it more closely. What they were then able to do was a traditional paternity comparison. Paternity tests use the exact same technology and type of DNA comparison that law enforcement has for decades."
Moore explains it's the same technology used to look up DNA profiles in the national database CODIS, which looks at 20 genetic markers. She says law enforcement would've compared two alleles, one from each parent.
"And one of those alleles at each location would have been a match, so they could have determined that he was the father of the suspect," Moore says. "It's really quite straightforward. And it's not a difficult process."
Again, Moore explains, even those 20 genetic markers are so unique and vary so much between individuals, law enforcement can confidently say nearly no one else on the planet would have the same profile.
The affidavit says 'the Idaho State Lab reported that a DNA profile obtained from the trash and the DNA profile obtained from the sheath, identified a male as not being excluded as the bioiogical father of Suspect Profrle. At least 99.9998% of the male population would be expected to be excluded from the possibility of being the suspect's biological father.'
"Those are the ones we hear in court, the ones we hear law enforcement use as evidence, that there's a one in huge number chance that anybody else could be that DNA contributor or the parent of that DNA contributor," Moore says.
There may be more to learn beyond what was revealed in the affidavit.
"I think it's important to note that they did leave the investigative genetic genealogy out of the affidavit, which is proper," Moore says. "It is just a lead generator. It is a tip. It's a highly scientific tip, but it is not what leads to an arrest. It's not what leads to an eventual conviction in a court of law. And so they handled this exactly in line with what we've been seeing the judges ruling across the country in the cases where investigative genetic genealogy has been used, and they seem to be following that precedent that we've seen."
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