Bryan Kohberger Murder Investigation: How a Dirty Q-Tip and Late-Night Stakeout Led to Killer's Arrest

Confessed Idaho murderer Bryan Kohberger might still be a free man if not for one big mistake he made at the crime scene.

At Kohberger’s plea hearing in Boise last week, Latah County Prosecutor Bill Thompson detailed the investigation into the quadruple murders and how local police were able to track down the killer with the help of federal agents.

Thompson admitted that there were a number of holes in the investigation, but one thing that linked Kohberger, 30, directly to the crime scene — trace amounts of his DNA.

Upon entering the off-campus home near the University of Idaho on Nov. 13, 2022, Kohberger immediately proceeded from the second-floor entrance to the third floor, said Thompson, where his first two victims Madison Mogen, 21, and Kaylee Goncalves, 21, were laying in bed.

Goncalves tried to fight him off but was overpowered, and after stabbing the two young women to death, Kohberger then tried to leave the crime scene, Thompson said.

His plan changed after he crossed paths with Xana Kernodle, 20, on his way downstairs. He proceeded to stab her and her sleeping boyfriend Ethan Chapin, 20, to death, Thompson said.

Kohberger then fled the home, but left behind a piece of evidence integral to police identifying the former criminology student as a suspect.

“The defendant, as he left that room for whatever reason, ended up leaving behind the sheath for a KA-BAR knife. It was left on the bed next to Madison Mogen’s body,” Thompson said in court.

The sheath contained trace amounts of DNA, which alone couldn’t identify a suspect, but was enough to match with DNA from another man found in a national database – the suspect’s father.

“Law enforcement at this point were aware of Mr. Kohberger, had been accessing information about him and were trying to find him. They located him in Pennsylvania and did what’s called a ‘trash pull,'” Thompson explained in court.

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FBI agents worked with members of the sanitation department in the gated Pennsylvania community where Kohberger’s parents lived, where he had returned for the holidays, to take trash that had been set out for collection by the family.

That trash was then flown from Pennsylvania to the forensics lab run by the Idaho State Police.

“The lab experts there were able to identify DNA on a Q-tip as coming from the father of the person whose DNA was found on the knife sheath that was next to Madison Mogen’s body on the bed,” Thompson said. 

That was enough for a judge to sign off on an arrest warrant, and on Dec. 30, 2022, Kohberger was arrested at his parents’ home in Albrightsville, over 2,500 miles away from the scene of his crime. He was extradited back to Idaho and has spent the past 915 days in a jail cell.

Were it not for that knife sheath, however, prosecutors may have never been able to make a case against Kohberger, who Thompson said was otherwise meticulous in covering his tracks.

“The defendant has studied crime,” Thompson anoted in court. “In fact, he did a detailed paper on crime scene processing when he was working on his Ph.D., and he had that knowledge skillset.”

Kohberger is due back in court on July 23 for his sentencing hearing, after entering a guilty plea to all four murders on July 2.

The plea deal he signed suggests that he be sentenced to four consecutive life sentences for his crimes, as well as an additional 10 years for breaking into his victims’ home.

In accepting that deal, prosecutors agreed not to seek the death penalty, although Kohberger’s sentence will ultimately come from the judge overseeing the case.