DNA from Bryan Kohberger, the suspect accused of murdering four Idaho college students last year, was a “statistical match” to DNA found at the crime scene, state prosecutors said in new court documents.
Kohberger, a 28-year-old former criminology student who attended a nearby university, was arrested in late December, weeks after the stabbing deaths of Ethan Chapin, 20; Madison Mogen, 21; Kaylee Goncalves, 21; and Xana Kernodle, 20, whose bodies were found by another roommate on Nov. 13.
Authorities have said he was identified through surveillance video, cell phone tracking and DNA, which was left on a knife sheath found in one of the victims’ beds near her body.
New court docs say Kohberger’s DNA is a match
Investigators announced previously that they had linked DNA found at the murder scene to DNA from Kohberger’s father pulled from trash at the family home in Pennsylvania.
The new court filings reveal that DNA from a swab of Kohberger’s cheek has been directly tied to the DNA on the knife sheath.
“The comparison showed a statistical match – specifically, the (short tandem repeat) profile is at least 5.37 octillion times more likely to be seen if Defendant is the source (of the DNA) than if an unrelated individual randomly selected from the general population is the source,” the filing said.
The DNA from the knife sheath came from a single male source, authorities have said.
How investigators used DNA to link him to the crime
The new court filings shed light on how investigators got the initial DNA match that led them to Kohberger. They started with the genetic material located on the knife and tried uploading it to the Combined DNA Index System or CODIS, a database of DNA from people convicted of crimes, people who have been arrested, and DNA from other crime scenes. But they didn’t get a hit.
Next, investigators used a process called Investigative Genetic Genealogy. They uploaded a profile of the DNA sample to a public database where people can upload their own DNA profiles generated by services like Ancestry.com and 23andMe. They built out a family tree based on what they found and used other sources of information like social media and birth and death certificates.
After the IGG pointed investigators toward Kohberger, they obtained trash from the family home through a search warrant and performed an analysis to confirm that the DNA belonged to the father of the person whose DNA was on the knife sheath. Later still, investigators took a swab from Kohberger’s cheek and made the direct comparison.
“Specifically, with respect to DNA, an STR DNA analysis found Defendant’s DNA matched the DNA collected from the Ka-Bar knife sheath,” the court filing said.
Prosecutors asked the judge to block the release of the information in the Investigative Genetic Genealogy to protect the identities of “hundreds” of Kohberger’s relatives. They said it isn’t relevant to the prosecution because they will be relying on the direct DNA match, not the family tree.
“The IGG process pointed law enforcement toward Defendant, but it did not provide law enforcement with substantive evidence of guilt,” the filing says.
Prosecutors plan to use the DNA link as evidence during Kohberger’s upcoming murder trial, they said in the court filing.
DNA PROFILING:How did investigators use DNA profiling to identify the suspect in the Idaho student killings?
Stabbing deaths rocked local community
The stabbing deaths at the rental house near the University of Idaho, and the subsequent weeks without any leads being made public rocked the community. Officials announced they would raze the house where the crime happened as “a healing step.” The university said it will memorialize the four students with scholarship funds and an on-campus memorial.
“These tragic murders took four young, vibrant lives from our community. Nothing we do can bring them back,” Idaho State Police Colonel Kedrick Wills said when Kohberger was arrested.
Kohberger was indicted on murder and burglary charges by a grand jury, but the proceedings and most of the evidence remain secret. He could face the death penalty if convicted. A judge entered not guilty pleas on his behalf.
Investigators say Kohberger was a Ph.D. student in criminology at Washington State University across the nearby state line from the University of Idaho.
TIMELINE:A mystery, no leads, then a break in the case: Timeline of the Idaho student murders investigation
Contributing: Trevor Hughes and Terry Collins, USA TODAY
