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Crime News University of Idaho Murders

Cheek Swab of Idaho Murder Suspect Bryan Kohberger Directly Links His DNA to Found Knife Sheath, Prosecutors Say

The DNA found on the knife sheath was at least 5.37 octillion times more likely to be Kohberger's than a random member of the public, prosecutors said in a new court filing. 

By Elisabeth Ford
Suspect In University Of Idaho Students' Killings Arrested

University of Idaho murder suspect Bryan Kohberger has been directly linked to the quadruple slaying at an off-campus house by DNA from the knife sheath found at the crime scene, according to a new court filing.

Law enforcement officials used genetic genealogy to link Kohberger — a 28-year-old former doctoral student from Washington State University — to the Ka-Bar knife sheath that was found on the bed next to the bodies of 21-year-olds Madison Mogen and Kaylee Goncalves, Latah County prosecutors said in a June 16 motion for a protective order.

RELATED: Judge Enters Not Guilty Pleas for Suspect in Stabbing Deaths Of 4 University of Idaho Students

The sheath was found partially under Mogen’s body and the comforter on the bed.

Investigators found that the DNA was at least 5.37 octillion times more likely to be Kohberger's than a random member of the public, the document states.

The FBI had originally entered the DNA profile from the sheath onto publicly available genealogy sites to find a match.

Bryan Kohberger sits with his attorney

"The FBI went to work building family trees of the genetic relatives to the suspect DNA left at the crime scene in an attempt to identify the contributor of the unknown DNA," the document said, adding that a tip was sent to investigate Kohberger.

The tip was enough to look into Kohberger but did not “provide law enforcement with substantive evidence of guilt,” according to the motion.

RELATED: "I'm Not Going To Scar Myself": Mom of University of Idaho Murder Victim Says She'll Try To Avoid Graphic Testimony

When law enforcement compared a DNA sample from trash recovered at the Kohberger family’s Pennsylvania home to the DNA found on the crime scene evidence, it indicated that “the DNA found on the trash belonged to the biological father of the individual who left the DNA on the Ka-Bar knife sheath,” according to the filing.

They then collected DNA from a cheek swab done on Kohberger, and when directly compared with the DNA found on the sheath, it was a “statistical match.”

Ethan Chapin, Xana Kernodle, Madison Mogen and Kaylee Goncalves

Prosecutors said in the filing that they do “not intend to enter” the ancestry data into evidence at the trial.

“Instead, the State has relied on and will continue to rely on the STR DNA analysis comparing Defendant’s DNA to the DNA on the Ka-Bar knife sheath to establish Defendant’s guilt,” the motion states.

Kohberger was arrested on Dec. 30, 2022 for the Nov. 13 stabbing deaths of Goncalves and Mogen, as well as Xana Kernodle, 20, and her boyfriend Ethan Chapin, 20. He has been indicted on four counts of first-degree murder.

His lawyer entered a not guilty plea on Kohberger’s behalf. His trial is scheduled for Oct. 2.