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Investigators untangling the Idaho student slayings face a ‘daunting task’: Parsing the DNA

Victims' families and the public are growing impatient with police investigating the University of Idaho stabbings. But analyzing evidence could take weeks.
Photo illustration of the four slain University of Idaho students, the door to the house where the murders occurred, finger prints, police caution tape, and evidence rulers.
More than three weeks have passed since four University of Idaho students were stabbed to death. Police have yet to name a suspect.Chelsea Stahl / NBC News; AP Images; Getty Images

The search for whoever fatally stabbed four University of Idaho students last month includes examining an enormous amount of biological and digital evidence, a kaleidoscope of potential clues — some obvious, some unseen and some that may lead to wrong answers. 

No suspect has been publicly identified, no weapon has been found, and police have said little about what they’ve learned, as the small college town of Moscow has become the focus of widespread grief, anger and speculation.

A break could come at any moment, from a confession or the thousands of tips submitted to police. Such tips led the city's police department to ask the public Wednesday for help tracking down the occupants of a white Hyundai Elantra in the early morning hours of Nov. 13, the day the students were found dead.

The people in the car, which may have been near the house where the students were later discovered, could have "critical information," the department said.

But in the absence of a sudden development, investigators are relying on forensic techniques to tackle a case, in a time-consuming process that appears unusually complex, according to a half-dozen experts in crime-scene analysis and evidence gathering.

“This is a case that only the most experienced crime techs can solve and answer,” said Jennifer Coffindaffer, who worked 25 years as an FBI agent and investigated violent crimes. “It’s going to take a long, long time.”

Coffindaffer and the other experts told NBC News that the forensic investigation may be complicated by the chaotic nature of the murders, the layout of the rented house where the victims were found and the likelihood that many students hung out or partied there. Collecting and processing hundreds of DNA samples and then looking for a potential suspect’s genetic profile could take weeks or months, the experts said. 

“I know it’s frustrating to people, but murder investigations are not a spectator event,” said Howard Ryan, a former commander of a crime scene unit in the New Jersey State Police who is now a consultant for law enforcement. “People are influenced by TV shows. They believe that these events and processing and work happens at a much more rapid pace and results are obtained much quicker than they really are.”

Although blood can be a crucial source of DNA, investigators don’t know from the start which is the victims’ and which could be from a suspect. The same thing goes for other potential clues left behind. So investigators have to collect a lot of specimens.

“You can’t assume each drop of blood is from the same person,” said David Carter, a professor of criminal justice at Michigan State University and former Kansas City, Missouri, police officer who specializes in homicide investigations and intelligence. “You have to sample them all and analyze them all to see if they belong to victims or a suspect. It’s very time intensive. They’re trying to find hairs, footprints from shoes, fingerprints — anything like that.”

Authorities in Idaho could be waiting on the outcomes of forensic analyses, which can take weeks or months to complete, he said.

“They’ve got to look at it all,” Carter said. “It’s laborious. Really laborious.”

Flowers are left at a make-shift memorial honoring four slain University of Idaho students in Moscow, Idaho.
As the University of Idaho campus mourns, students remain worried about their safety.Tim Stelloh / NBC News

Each day that passes disheartens victims’ families, fuels impatience from the public and adds to the pressure on authorities.

The Moscow Police Department has called in the state police and FBI for help, charted the victims’ final hours and ruled out a number of people as suspects, including two roommates who were in the house at the time of the Nov. 13 killings. They’ve chased down unsubstantiated leads and tamped down speculation and rumors that have circulated in the absence of news. 

Police have also faced criticism from students and the local community for not providing more information about their investigation, including why they believe the stabbings were a “targeted attack.” Police have also released conflicting statements about the ongoing threat to the public.

Moscow police have said they recognize how frustrating the lack of news can be for the families and the public, but do not want to jeopardize the case.

“We are at that point in the investigation where we’re still gathering information, we’re still gathering tips, we’re still gathering evidence, we’re still doing everything we need to do,” Moscow Police Chief James Fry said in a video posted online Tuesday afternoon.

The Moscow killings occurred in a three-story, six-bedroom rented house, about a half-block from the University of Idaho campus. Three of the victims —  Madison Mogen, 21; Xana Kernodle 20; and Kaylee Goncalves, 21 — lived in the house. The fourth, Ethan Chapin, 20, was Kernodle’s boyfriend and was staying the night, police said. 

Two victims were found on the second floor and two on the third floor, police said. All four were likely asleep and each were stabbed multiple times, some with wounds that suggested they’d fought back against their attacker, police said, citing the coroner. Two roommates on the first floor slept through the killings, police have said. 

Investigating a crime like this begins with securing the scene, which likely has already been walked through by witnesses and the first patrol officers to arrive, experts said. Then investigators document everything they see — taking photographs, writing notes and creating 3D scans. Next, investigators move through the scene, swabbing surfaces for DNA and fingerprints, collecting blood samples and looking for clues in where the blood was found.

“With four victims and multiple bedrooms and multiple floors of a house, each room becomes a scene unto itself,” Ryan said. 

Many basic details have not been released, including the exact location of each victim, the order in which they were killed and the extent of each of their wounds. Police have also not publicly theorized how the killer entered and exited the home, but say there were no signs of forced entry or property damage. Investigators also said none of the victims were sexually assaulted. The weapon is believed to have been a fixed-blade knife.

Moscow police say they’ve collected 113 pieces of evidence but have not provided more details. They said they’ve also received more than 5,000 tips by email and voicemail. More than 1,000 “digital media submissions” have been provided to the FBI.

“We’re putting the pieces together, and I think when that picture is done, I think we’ll have a real clear definition of what occurred and where to go,” Aaron Snell, an Idaho State Police spokesman, told NBC News last week.

The FBI has assigned nearly 50 investigators to the case, while the state police has placed more than a dozen investigators and forensic experts to provide testing and analysis to help Moscow’s team of six detectives.

The department declined to say how long the process of examining evidence would take or answer other questions about the investigation.

Underlying the case is a sobering statistic: U.S. police made arrests in less than half of homicides in 2021, according to FBI data. An analysis of 2019 data from the bureau shows authorities are 25% more likely to solve stabbings than shootings, but that data is from less than half of the nation’s roughly 18,000 departments, said Steven Briggs, a professor of political science at North Dakota State University who studies “clearance rates,” or the number of cases closed by arrest and other means.

Researchers aren’t sure why stabbings may be more likely to be solved, but Briggs said that “homicides committed with sharp objects often bring the victim and offender into close contact whereas those committed with firearms can occur in close proximity or greater distances. This may make the identification of a suspect easier or more likely for bystanders or other witnesses when they are present.”  

The lack of an arrest has unsettled the University of Idaho, where many students have chosen not to return to campus for the remainder of the semester, or are asking for police escorts around campus. Family members of victims have also expressed frustration.

Steven Goncalves, Kaylee’s father, said in an interview last week that the lack of information released by the police has made him fear the investigation will lose momentum. 

“Don’t let this go cold like some of these cases that we’ve seen around. That just makes the pain last even longer,” Goncalves said. 

Officers investigate a homicide at an apartment complex south of the University of Idaho campus on Sunday, Nov. 13, 2022.
The apartment house in Moscow, Idaho, where four students were stabbed to death held an enormous amount of biological evidence, experts say.Zach Wilkinson / The Moscow-Pullman Daily News via AP file

Experts stress that investigations like this one are nearly impossible to work quickly given the level of evidence that needs to be processed and the potential for mistakes. 

Peter Yachmetz, a retired FBI agent with three decades at the agency specializing in security, said the samples could number in the thousands, and may not even be from the victims or the killer. A college apartment house can have a lot of people coming and going or staying the night. “So, who could have left that DNA evidence? It’s a pretty daunting task,” Yachmetz said.

Before getting answers about DNA, investigators seek clues in the location of blood. 

If there isn’t a lot of blood far from the body, it could show that that there wasn’t much of a struggle — perhaps because the victim was killed while they slept, experts said. Blood leading away from a body could mean the killer was injured. If the killer got blood on themselves, then they would likely try to remove it using towels, clothing, toilet paper, a sink, even the washing machine. How messy they were could provide insight into whether the killer had planned the crime or acted in the moment. 

Investigators “try to identify the blood drops that don’t fit the larger pattern,” said Greg Hampikian, a DNA expert at Boise State University and the executive director of the Idaho Innocence Project. “That could be either from dripping from a knife or a hand as the person’s walking away or from an injury to the assailant.”

If the assailant is not wearing gloves, their hands likely touched things that investigators can try to collect DNA from, Hampikian said.

Swabs and other items taken from the scene are sent to a crime lab, where scientists look for signs of DNA. Finding enough genetic material to build a full DNA profile of a suspect can take days. Investigators also try to get DNA swabs from a wide array of people. Some, including the victims and those who have been ruled out as suspects, are considered “exclusionary.” But experts also recommend getting swabs from anyone else investigators interview, just in case. 

DNA profiles from potential suspects are run through a federal database collected by law enforcement agencies around the country of people arrested for or convicted of crimes. Profiles collected from unidentified suspects in unsolved crimes are also in the database, known as CODIS. A match can lead authorities to a suspect, who they must then locate and confirm a match with, a process that can take days or weeks.

If there is no hit in CODIS, then investigators can use other methods to find a DNA match. One method that has become widespread in recent years is genetic genealogy, in which investigators enter an unknown suspect’s DNA profile into databases compiled by consumer services typically used by people to learn about their ancestries. That search could reveal relatives of the unknown suspect. Then, using public genealogy records, they build family trees that could lead them to the killer. That process can take weeks or months.

Biological evidence is just one aspect of the forensic investigation. 

Typically, the victims’ computers and phones are scanned for clues in emails, text messages, social media posts, internet searches and photos. Phones can also reveal the victims’ movements.

Investigators can also get a judge’s permission to ask Google and other tech companies for information about phones that were in the area of the murders, a tool known as geofence warrants. This method has led police to suspects on all sorts of crimes, from murder to burglary. 

Ryan said he assumed that geofence warrants are being used in the Idaho case, along with other kinds of digital dragnets.

But he’s not surprised that police in Idaho have not said whether they’re doing any of this.

“As investigators we don’t owe the public real-time updates. Investigations are sometimes done very quietly and clandestine, and sometimes it has to be that way,” Ryan said. “Maybe they have someone under surveillance and they are waiting for results. Maybe they have someone. Or maybe they have nothing.”

CORRECTION (Dec. 7, 2022, 4:02 p.m. ET). An earlier version of this article misstated Steven Briggs’ department at North Dakota State University. He is a professor of political science, not criminal justice.