BOISE, Idaho — Just days after sentencing in the most closely watched and scrutinized case of Bill Thompson’s decades-long legal career, he acknowledged that prosecuting Bryan Kohberger, who pleaded guilty to murdering four University of Idaho students, might not have been possible if the killer had not left his DNA at the crime scene.

Without that “critical” piece of evidence, Thompson told the Idaho Statesman in a phone interview, the state could have struggled to bring charges, let alone make an arrest of its only suspect.

“From our perspective as prosecutors, the DNA was critical to the strength of the case for trial purposes,” Thompson said.

After sentencing, lead investigator Moscow Police Cpl. Brett Payne expressed confidence that law enforcement would have ultimately arrived at Kohberger, who drove his white Hyundai Elantra to commit the stabbings with a large, fixed-blade knife.

James Fry, former Moscow police chief, told the Statesman the same, though admitted that the timeline likely would have extended by as much as several months before an arrest.

“There are a lot of white Hyundai Elantras out there,” Thompson said. “But if they stuck with it, eventually they would have found Mr. Kohberger’s car and made that preliminary connection.”

It wasn’t until investigators confirmed the paternal DNA match from trash retrieved at Kohberger’s parents’ home that the longtime Latah County prosecutor said he and his team felt they had the evidence needed to seek an arrest warrant. And trying to prove Kohberger’s guilt beyond a reasonable doubt without the link through his DNA found on a leather knife sheath — in addition to no known motive and no murder weapon — could have been insurmountable at trial.

“Yeah, I think that that’s fair to say,” said Thompson, in his 33rd year as the North Idaho county’s elected prosecutor. “We didn’t have to make that decision.”

Kohberger, 30, was sentenced last week to four consecutive life terms in prison after he reached a plea deal to avoid the death penalty. He has no chance of parole, and also waived his ability to appeal.

The four fatal stabbing victims were U of I undergraduates Kaylee Goncavles and Madison Mogen, both 21, and Xana Kernodle and Ethan Chapin, both 20. The three women lived in an off-campus home on King Road in Moscow with two other female roommates, while Chapin was Kernodle’s boyfriend and slept over for the night.

A number of questions remain in a case that generated international attention — including for Thompson, who was involved from the investigation’s first day. Before then, he’d not before visited that home or college neighborhood in Moscow, he said. But he stands behind the resolution of the case, which led to his putting off retirement.

As an example of what’s still a mystery, the order of the four victims’ deaths is not entirely clear, Thompson said. But he and investigators believe Goncalves or Mogen might have been Kohberger’s intended target, because it appears he entered the home and immediately went to the third floor, where the first attacks occurred.

And, as alleged by Goncalves’ older sister at sentencing, Kohberger may have used a second weapon in the murders. Her injuries included a “horizontal pattern,” ABC News reported, but that didn’t break the skin and weren’t fatal, Thompson said.

“There were injuries that appeared to have been caused by something other than the knife, although it could have been the knife,” Thompson said, relying on the assessment of the medical examiner in Spokane, Washington, who conducted the autopsies. “I don’t think we can exclude the possibility that there was an additional weapon involved.”

Autopsy reports are confidential in Washington, he noted. But he shared generally that the toxicology results for the four victims, which have not before been released, showed “varying levels of alcohol intoxication” and “no evidence of any illegal drug use at all,” Thompson said.

Just two of the four victims — Goncalves and Kernodle — had defensive wounds, he said.

Unanswered questions

Among the people police interviewed during the investigation was a woman who drove for the food delivery service DoorDash and brought an order of Jack in the Box to Kernodle at about 4 a.m. the morning of the murders. After an unrelated traffic stop in September 2024, she told Pullman police that she expected to testify, and believed she “saw Bryan” and had “parked right next to him.”

Thompson confirmed her identification and said prosecutors intended to call her as a witness had there been a trial, but only to help establish the timeline of the murders. Based on neighborhood video surveillance footage, the woman did not come across Kohberger or his car, he said. Instead, she likely saw a light-colored SUV, Payne wrote in a redacted, but now public, police report after he interviewed the driver 10 days following the homicides.

“The vehicle and person she saw that she thought might be the killer is not Mr. Kohberger,” Thompson said. “That was a different vehicle, a different person at a slightly different time, from what the investigators were able to see from the security video.”

The only person to see Kohberger that morning was Dylan Mortensen, one of the two surviving roommates. She told police that she opened the door to her second-floor bedroom and saw a man clad in black wearing a mask over his nose and mouth, with bushy eyebrows, who walked toward the second-floor sliding glass door carrying a “container” of some kind.

Investigators still don’t know what Kohberger had in his hands, but Mortensen’s recollection of the events was consistent over several interviews, Thompson said. She also reported that the man in the home later identified as Kohberger saw her after killing her roommates, but left anyway.

“From what Dylan described, I have a hard time imagining that the killer did not see Dylan,” Thompson said. “At that point, he’d been in the house probably longer than he planned, and he had killed more people than he planned. … It wouldn’t surprise us that the killer was scared at that point and decided they had to leave, not knowing if law enforcement already had been called.”

Mortensen delivered a tearful victim impact statement at Kohberger’s sentencing hearing last week. Seated at the prosecution table, she described in detail the personal trauma she continues to endure over the deaths of her four friends and the events of that night. Thompson leaned forward beside her to block Kohberger’s vantage, and did so at her request, he said.

“Powerful doesn’t come close to a strong enough word to describe how that felt — the strength that she showed, the pain that she has been suffering,” Thompson said. “Everything that she shared and talked about is so honest and so sad. We were very proud of her for being able to do that.”

Ka-Bar knife at trial

Thompson initially said the prosecution intended to call as witnesses at trial two members of Kohberger’s immediate family. The defense won a ruling from Judge Steven Hippler to allow his parents and two older sisters to attend the entire trial if they chose.

Thompson and his team considered calling Kohberger’s older sister Amanda, and either his mother or father. Kohberger’s parents attended his plea hearing earlier this month, while his mother and Amanda were present for his sentencing. Both of them cried during victim statements.

In the end, had the murder trial moved forward, prosecutors settled on calling none of them, Thompson said.

“As we continued to review them as potential witnesses, we decided that they just simply weren’t the best witness to show what was going on,” he said. “The parents were understandably protective of their son, and the sister really didn’t seem to have anything specific that she could contribute.”

Those family members were interviewed by investigators in January 2024, according to Moscow police reports. They also spoke with law enforcement immediately following the raid and arrest of Kohberger at his parents’ home in Pennsylvania in late December 2022, which included a search warrant for a variety of Kohberger’s belongings.

None of what they shared was “substantively incriminating” during those discussions, which Thompson called “casual conversation.”

“To the extent you have casual conversation when the police execute a search warrant in the middle of the night,” he said.

Taken from the home were dozens of items, according to a Pennsylvania search warrant return record, including several academic textbooks, several knives, a handgun, notes from Kohberger to his parents, and “ID cards inside glove inside box.”

The two “ID-type cards” were of two women who were former co-workers or acquaintances of Kohberger’s from several years earlier, Thompson said. At least one of them was from when he worked as a part-time security officer at the Pleasant Valley School District. Kohberger graduated from the district’s high school, and his parents also previously worked in the district.

“Both of the individuals were contacted by investigators,” Thompson said. “They don’t know how Mr. Kohberger ended up with those items, and they had not been harmed or threatened or anything themselves.”

What investigators never recovered — either in Pennsylvania, or at Kohberger’s graduate student apartment in Pullman — was the knife sharpener he bought on Amazon in March 2022, when he bought the Ka-Bar knife and sheath, Thompson said. And they never found the knife used in the murders.

At trial, however, prosecutors intended to present a Ka-Bar knife and sheath to the jury for demonstrative purposes, Thompson said. Investigators “replicated what the Amazon purchase records showed that Mr. Kohberger had done,” he said.

‘It met the elements’ for the death penalty

If the defense had not contacted the prosecutors about a plea deal, Thompson said he was confident in their evidence to obtain a conviction of Kohberger on four counts of first-degree murder. He and his team had no hesitation about seeking the death penalty, he said.

“Our thought is that this case is on track for trial, and if that’s where it goes, that’s where it’s going to go,” Thompson said. “And we’re going to do our best job to present everything that we believe is legally relevant to help the jury make that decision.”

Thompson has received criticism — mainly from the Goncalves family, but also from Kernodle’s father — for striking a deal with the defense that bypassed trial and a possible death sentence for the man who murdered their daughters. Thompson said he doesn’t hold strong personal feelings about the death penalty, recognizes it is the will of the people in the state through the Idaho Legislature, and does “accept it at face value.”

The prosecution absolutely would have tried to get it if the case had gone to trial, he said.

“This certainly was a case where the death penalty was appropriate,” Thompson said. “If we ended up going through trial into a penalty phase, I think under the law it met the elements.”

With the Kohberger case now finished, Thompson plans to reassess his remaining time in office. He already considered retiring last year, but felt compelled to see the prosecution of Kohberger through, including trial, and ran for a ninth term to continue his tenure in the role since 1992.

“I simply couldn’t walk away. I couldn’t leave office,” he said. “This case, it was too important. The stakes were too high, so I ran for reelection and nobody ran against me. I can’t imagine why.”

Thompson said he now may consider retiring before his current term ends at the start of 2029. Whenever he calls it a career, he said, he would leave with a “great deal of satisfaction knowing that we’ve been able to bring this case to a conclusion.” He called it a “trying experience” overseeing the high-profile case over more than two and a half years.

“I think that we did our job, and we had the opportunity to do in a way to really give some immediate finality, which wouldn’t have happened if we had to go through trial,” Thompson said. “We’re pleased and relieved that the community and the victims’ families aren’t going to have to continue to live through this, and relive this during a trial.”

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