After students were stabbed to death in a house near a college campus, investigators finally brought leads for a new, breakthrough DNA technique. Forensic evidence and data were gathered by the investigators.

In November, four University of Idaho students were found dead in a house they had rented in Moscow. Investigators from The New York Times credit Rajah Bose…

In the weeks following the incident, a group of investigators diligently scoured the area near the University of Idaho campus, but they were unable to locate the murder weapon or identify a suspect. Despite their best efforts, the slaughtered bodies of University of Idaho students remained undiscovered in a house nearby.

The authorities were depleting their opportunities, combing through the histories of individuals who had the slightest conceivable links to the case in a confidential manner. Publicly, they were reassuring concerned residents in the small college town that they were making advancements.

Each one proved to be a fruitless path. They scrutinized a white supremacist. They examined sex offenders. They investigated a man previously accused of brandishing a knife. They probed into a woman who had previously faced charges for assaults in the area. Additionally, they expanded their search to include a man from another state who had a history of sending harassing messages to women, although he had only visited Idaho on two occasions in his lifetime. During the initial fortnight of December, investigators directed some of their attention towards the victims’ classmates.

After weeks of sifting through an extensive range of evidence that seemed to lead nowhere, investigators announced the arrest of Bryan Kohberger in late December on the other side of the country. It was only after turning to an advanced DNA analysis method that they were able to identify him as a Ph.D. Student from a nearby university.

The quadruple murder investigation led the officers from local, state, and federal agencies into extraordinary territory, as key details discussed by individuals familiar with the investigation in interviews and recently obtained records emerged after a gag order had already been issued.

The investigation has shown to what degree law enforcement investigators have come to rely on the digital footprints left by ordinary Americans in nearly every facet of their lives, using traditional sleuthing techniques as well as technology. They play various roles in genealogy, amateur investigation, and driving along the streets of the city, while carrying a cellphone, shopping online, and even selling cars.

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The accused killer had connections with four young people who were killed. The family members of the victims remain unaware of any prior connections to the accused. Investigators have yet to uncover a possible motive for this day. Mr. Kohberger, the accused, previously contended through his lawyer that he would be exonerated, but now he has declined to enter a plea and has been indicted on four counts of murder.

The community’s persistent demand for answers resulted in a lengthy and arduous process of identifying and apprehending a suspect, spanning over six weeks. Throughout these weeks, frustration grew and evidence was meticulously examined.

The Moscow Police Department initially described the attack as “targeted” and assured the residents that there was no risk to the public, despite the lack of indication as to why or who had committed the attack. Ethan Chapin, Xana Kernodle, Kaylee Goncalves, Madison Mogen, and 21-year-olds were stabbed to death in their bedrooms overnight. The first 911 call came in around noon, seven hours after the murders.

Following the homicides, on November 16, three days later, the police chief, James Fry, stated at a press briefing, “We are unable to declare that the community is without any danger.”

The department, which had only a few dozen officers, sought assistance from the Idaho State Police and the F.B.I., Enlisting dozens of additional investigators. Meanwhile, some individuals scoured the town for surveillance footage, while forensic teams meticulously examined evidence from the bedrooms, captured photographs near the back entrance of the house, and diligently searched for footprints.

Investigators quietly ran down details on thousands of vehicles, including the owners’ addresses, license plate numbers, and colors of each sedan. They were on the lookout for a certain type of Nissan Sentra vehicle, ranging from the 2019 to 2023 models, following a week of killings, as shown in the records.

The Moscow police asked law enforcement agencies to look for a different type of car, similar in shape to a white Hyundai Elantra model from the years 2011 to 2013, in order to obtain more clarity and further scrutinize the video footage produced on November 25th.

In the field of criminology, Mr. Kohberger relocated to the area in order to commence his Ph.D. Studies in 2022. Once they discovered a vehicle registered under Mr. Kohberger’s name, campus law enforcement officers initiated a search within their archives for Elantras that were registered at Washington State University, which is situated just on the other side of the state border.

According to a court affidavit, in Moscow, the primary focus of their search was not on the vehicle itself, but rather on a 2015 model which they inspected with greater scrutiny. Additionally, they paid a visit to the parking area close to Mr. Kohberger’s apartment during the early hours of November 29th to examine his car.

Only a few responses provided the necessary information. The individuals who owned the car were clearly interested in the legal and ownership history.

In a city that hadn’t witnessed a homicide in seven years, individuals started securing their doors, obtaining pepper spray, and inquiring on social platforms about how such a bold murderer could persist undetected for such a lengthy period. Meanwhile, students at the University of Idaho were getting ready for their final exams, creating a constant feeling of unease in the atmosphere.

The investigators expanded their search and collected additional records and data as they sought cellphone data for all the phones that were pinged by the cell towers within a half-mile radius of the victims’ house, from 5 a.M. To 3 a.M. They already had the email correspondence and social media accounts of the bank victims, as well as the collected data from their search warrants.

Five detectives requested new video surveillance footage, seeking recorded footage from the days before and after the killings, specifically focusing on U.P.S. Delivery trucks.

After obtaining data from Ms. Goncalves’s Tinder account the following day, detectives asked for specific details on 19 account-holders, including private information such as credit card details and their locations, and associated the accounts with images, pictures, or videos.

Orin Kerr, a law professor at the University of California, Berkeley, stated that a single warrant can target 19 different individuals, allowing the inquiry to go much broader in terms of information search than an ordinary request would permit.

“You couldn’t obtain a single search warrant for 19 residences,” he stated.

They spread out and commenced searching for nearby establishments that could have potentially sold the weapon. Initially, they discovered a Ka-Bar knife sheath, adorned with a U.S. Marine Corps emblem, in close proximity to two of the victims. This particular item served as a crucial piece of evidence that the investigators were also analyzing.

Mr. Kohberger’s name came up in records, including those from Japan, if it is unclear whether they are redactions. He had connections to the Washington and Idaho areas, including others who were far away — while seeking specific purchase histories, users focused on a series of knives on eBay. A follow-up request was made to Amazon to order the account histories of holders who had purchased such knives.

The overall data track was demonstrating enormous growth, showing the extensive breadth of consumer data that can be accessible to law enforcement agencies at the stage when they are hunting for bread crumbs on consumer platforms.

Mr. Kerr mentioned, “One could argue that we are entering unfamiliar terrain.” “There are numerous precedents available for novel legal inquiries.”

Although they did not find a match, as per information provided by three individuals familiar with the matter, the sample was analyzed using the F.B.I.’S extensive database, which houses numerous DNA profiles of previous lawbreakers. Simultaneously, the DNA collected from the crime scene was being analyzed. During the examination of the knife sheath, forensic teams discovered DNA that did not match any of the residents of the house.

In contrast to the data provided by the websites, law enforcement has the ability to compare DNA samples from crime scenes by utilizing a feature that allows users to track their lineage and familial connections through their own genetic material on certain genealogy websites. Among the increasing number of genealogy websites, there are platforms dedicated to assisting individuals in retracing their family history and identifying their relatives based on their own DNA. Although primarily utilized for solving cold cases rather than ongoing murder investigations, investigators decided to experiment with the method of genetic genealogy at that specific juncture.

The alleged Golden State Killer had been linked to a series of sexual assaults and homicides years prior in California, and investigators in 2018 managed to apprehend a suspect in one of the most renowned applications of genealogy in resolving an unsolved crime. Detectives can assist in constructing a genealogical chart based on DNA found at the crime scene and pinpoint a potential offender by analyzing DNA matches with distant relatives who have voluntarily participated in the system.

Once a suspect is identified, a direct genetic comparison can be utilized as verification prior to conducting an apprehension.

Country authorities across the say that the use of mass genealogy databases has raised concerns about privacy and whether limits should be placed on how this method is used. With few formal regulations in place, they argue that these databases have the potential to produce leads that are otherwise unattainable through traditional investigative efforts.

Barbara Rae-Venter, a genealogy consultant who worked on the Golden State Killer case, said that there is now a growing interest in using DNA genealogical investigations to solve not only active crime cases but also cold cases.

“That is why the Idaho situation is so captivating,” she expressed.

In order to generate a more comprehensive DNA profile from the sheath knife, the State Police of Idaho contracted with Othram, a private company based in Texas, which had the ability to set up and operate a laboratory for examination.

The F.B.I. Personnel who worked with the Othram profile had conducted an investigation with two familiar individuals, as per the information obtained. The investigation involved spending days building a family tree, which started with a distant relative.

Investigators discovered that Bryan Kohberger, a student at a university located eight miles away from the murder scene, owned a white Elantra, according to records obtained on the morning of December 19th.

Mr. Kohberger had already completed his semester and was on his way out of town when he was stopped twice by the police for tailgating. He had driven home to Pennsylvania with his father. After describing altercations with a professor, he was terminated from his position as a teaching assistant, prompting agents to start thoroughly scouring his background.

The killings took place around two in the morning when the cell networks were possibly turned off. However, his phone was active in the early morning hours of November 13th, which further fueled their suspicions. Investigators received and requested Mr. Kohberger’s cellphone records on December 23rd.

The genetic material on the knife cover belonged to a near relative of whoever had left genetic material. The laboratory was capable of making a groundbreaking determination by comparing the substance with their initial genetic profile. Officials in Pennsylvania were able to recover some garbage from the family home of Mr. Kohberger, and they sent it to the forensic laboratory of the Idaho State Police four days afterwards.

Mr. Kohberger was apprehended on December 30th

“Declared Mr. Fry, the head of the police, ‘But we still need to remain watchful, correct?’ ‘We have a person under arrest who perpetrated these dreadful offenses, and I firmly believe our society is secure.'”

This version of the article appears in print on Page 1, Section A of today’s edition of The New York Times, titled “Detectives Break Logjam in Four Student Deaths in Idaho.” Subscribe for reprints or order a copy of Paper Today.