Bryan Kohberger, the man charged with murder in the fatal stabbings of four University of Idaho students, bought the same brand of knife that police suspect was used in the violent crime in November 2022, according to a new court filing.

In March 2022, Kohberger ordered a Ka-Bar knife with sheath and a sharpener from Amazon, the prosecution alleged in the legal brief, which was filed Monday but not made public until Wednesday. Detectives found a Ka-Bar brand leather knife sheath that included the U.S. Marine Corps stamped insignia at the crime scene in Moscow next to one of the victims and later discovered DNA on its button snap, according to a probable cause affidavit.

Assisting with the high-profile case, the FBI used an advanced forensic technique called investigative genetic genealogy, or IGG, with the knife sheath DNA to initially land on Kohberger as the suspect in late December 2022, prosecutors previously said. After Kohberger’s arrest 12 days later in Pennsylvania, police and prosecutors allege the DNA was matched directly to Kohberger through a swab of his cheek.

The four U of I student victims were Kaylee Goncalves, 21, of Rathdrum; Madison Mogen, 21, of Coeur d’Alene; Xana Kernodle, 20, of Post Falls; and Ethan Chapin, 20, of Mount Vernon, Washington. The three women lived in the Moscow home with two other young women who went physically unharmed; Chapin was Kernodle’s boyfriend and stayed over for the night.

Each victim died from stab wounds and sharp-force injuries caused by an edged weapon, believed to be a large, fixed-blade knife, Latah County Coroner Cathy Mabbutt previously said. Just days into the sprawling homicide investigation, the Idaho Statesman was first to report that police were canvassing area hardware stores asking about any recent sales of fixed-blade knives.

Kohberger, 30, is charged with four counts of first-degree murder, and prosecutors intend to seek the death penalty if a jury finds him guilty. He is a former graduate student at Washington State University in Pullman, Washington. In summer 2022, Kohberger moved from Pennsylvania, where he grew up, to Washington to attend WSU’s doctorate program of criminal justice and criminology, according to court records.

After a court hearing in November 2024 in Boise, Steve Goncalves, father of victim Kaylee Goncalves, told the Statesman in an interview that he was informed of evidence that Kohberger bought a Ka-Bar knife before he relocated to the West for graduate school.

“I think he had thought about this crime immensely, planned it, and I think the facts will bear that out,” Steve Goncalves said. “I’ve been told the murder weapon was purchased in Pennsylvania. (If) you come out with that, then you’re coming with a plan.”

NBC’s “Dateline” previously reported Kohberger purchased a Ka-Bar knife, but cited only unnamed law enforcement sources.

Kohberger’s capital murder trial is set for this summer in Boise, starting with jury selection in late July. Opening statements are expected to begin by mid-August.

Prosecution wants Amazon data admitted. Defense calls it ‘cherry-picking’

Latah County Senior Deputy Prosecutor Ashley Jennings in the recent filing pushed back against a defense motion filed last month — aimed at excluding the prosecution’s use of information obtained from Amazon at trial — arguing that given the knife was purchased before the killings it is “more probable” the Ka-Bar sheath found on Mogen’s bed was Kohberger’s.

Kohberger “appears to argue that the evidence of defendant’s Amazon.com click history is not relevant,” Jennings wrote. “That is not the case.”

It remains unknown if police have found the weapon they believe was used to kill the four students. Kohberger’s defense has said repeatedly in court that their client has no connection to the victims and is innocent of the crimes for which he stands accused.

The defense said the search warrants were overly broad, and resulting data “incomplete” and from a “household account shared by Mr. Kohberger and other family members.”

“Cherry-picking specific clicks or purchases out of an Amazon click-history removes all of the context,” read the filings signed by defense attorney Elisa Massoth.

In fact, investigators “narrowly tailored” their search warrant for Kohberger’s Amazon account and disclosed all of the data to the defense, the prosecution argued in response Monday. The account’s historic data showed “purchase of a Ka-Bar knife with sheath before the murders and his click activity indicat(ed) a search for a knife with sheath after the murders,” the filing read.

Prosecutors plan to use means other than Amazon click activity to connect the knife purchase — “and subsequent search inquiries for a replacement knife and/or sheath” — to Kohberger, including his financial activities, they added.

Investigators in the case limited their spring 2023 search warrant to Amazon account activity, including payment methods, cart items, wish lists, purchases and reviews of knives and accessories viewed by Kohberger from March 20 to March 30, 2022 and also from Nov. 1 to Dec. 6, 2022, prosecutors wrote. Amazon responded with the requested data in June 2023, and two weeks later prosecutors provided the same information to the defense, they wrote.

Kohberger shared Amazon account with family

Kohberger’s attorneys argued limiting Amazon data to specific items “takes things out of context” and could cause the jury to speculate about intent, they wrote. The filing also raised concerns about Amazon’s use of artificial intelligence and how it shapes customers’ behavior with recommendations, paid advertisements and the algorithm.

Let’s say someone on a shared Amazon account purchased a pair of binoculars. Without additional information, the defense argued, who initially searched for the binoculars or whether the search was triggered by advertisements or AI would be unclear.

Massoth added in the filing that other items bought around the same time would also “provide context to the intent of the purchaser.” If someone bought binoculars alongside a sleeping bag and tent versus night-vision goggles, zip ties and a stun gun it “could show a completely different intent,” she wrote.

But the prosecution argued AI technology wasn’t relevant. Jennings wrote that even if an algorithm suggested certain products that wouldn’t cause a customer to repeatedly — and over several days, she wrote — browse webpages related to Ka-Bar knives, sharpeners and sheaths.

“What is clear from the defendant’s filing, is that the defendant doesn’t like this piece of the state’s evidence and therefore would like to keep this piece of evidence from the jury,” Jennings said.

Another concern raised by the defense was the use of a shared Amazon account. When family members share an Amazon account — like in Kohberger’s case — purchases and searches gathered about the customer’s interests impact all of the account’s users, Massoth said.

“One person in a household’s interest in certain items, impacts the entire household account and attributed ‘click activity,’ ” she wrote.

Kohberger shared his account with other family members, Massoth said, so his account’s history could be influenced by AI-recommended items or other users. The prosecution addressed this concern in a footnote of its response.

Jennings said prosecutors recognize “the identity of the user making the inquiries is relevant,” according to the filing, and they don’t plan to rely solely on the click activity to connect Kohbeger to the knife purchase.

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