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A hearing in the Idaho student killings case focuses on genetic genealogy. Here’s why that may be important

A hearing Wednesday in the murder trial of Bryan Kohberger, the man accused of killing four University of Idaho students in November 2022, focused on the investigative genetic genealogy evidence in the case – an issue his attorneys have said is a key part of his defense.

In an early February filing, the defense asked the court to allow three defense experts and unnamed “criminal investigators” to view the investigative genetic genealogy, or IGG, evidence, which has been sealed.

“This request is grounded in Mr. Kohberger’s 6th Amendment right to effective assistance of counsel and counsel’s ongoing duty to investigate the case brought against Mr. Kohberger,” attorney Anne C. Taylor wrote. “Access to these materials is necessary to investigate how and when Mr. Kohberger was identified as a suspect.”

In response, prosecutors did not object to showing the material to the three defense experts, but did take issue with the vaguely termed “criminal investigators.” The prosecutors said they should at least be named and said the defense failed to make an “adequate” argument as to why they need to see the information.

Taylor said in court Wednesday the defense needed the IGG evidence to understand the full timeline of how police began to focus on Kohberger.

Latah County District Court Judge John Judge declined for now to give the criminal investigators extended access to the IGG material. He said he would rather the experts already approved to see the evidence give specific examples of what access needs to be given to other investigators and have a separate hearing on that.

“What I’d like to get is some justification for digging in deeper if necessary. I’m not sure it’s necessary but I’m going to keep an open mind about that.

Though minor in scope, Wednesday’s hearing to discuss the issue reflects the defense’s interest in closely examining the investigative genetic genealogy evidence and its use in the investigation.

The powerful forensic method has spread widely among law enforcement investigators over the past few years. It has been used to crack some of the country’s most frustrating cold cases, most notably the arrest of the Golden State Killer in 2018.

But genetic genealogy has rarely been tested in a courtroom setting to an intense degree. And questions remain about how investigators obtained and used the forensic technique in this case, as well as broader constitutional evidentiary and privacy concerns.

“This is still a very new investigative technique,” said Jennifer Lynch, the general counsel of the Electronic Frontier Foundation, a nonprofit organization that defends civil liberties online. “I think the public should have the ability to know more about how these sorts of searches are conducted so that we can ensure the police are not just willy-nilly collecting DNA from people and running them against consumer genetic genealogy databases.”

Here’s a look at how investigative genetic genealogy works generally, its relevance to the Idaho student murders case and why Kohberger’s defense has focused on it.

How investigative genetic genealogy works

Genetic genealogy is a practice that blends DNA analysis in the lab with genealogical research, such as tracing a person’s family tree.

Genetic testing companies like 23AndMe and Ancestry have made it easy for millions of people to take at-home DNA tests and learn more about their heritage, families and health traits. Neither site allows members of the public or law enforcement to access their database of genetic knowledge.

Still, consumers can upload their DNA file to other public websites, such as GEDmatch, to learn about connections to other people who have also uploaded their DNA files to the site. From there, users can comb through public information, like obituaries, birth certificates or social media profiles, to try to learn about their family heritage, such as informing adopted children about their biological parents.

The practice began with hobbyists interested in learning about their family histories but in recent years has expanded into the world of forensics to try to solve cold cases and other violent crimes.

In the realm of forensics, investigators occasionally come upon a crime scene with DNA evidence, such as blood or sperm, but no specific suspects. Investigators can take this unknown person’s DNA and compare it to DNA profiles in the FBI database CODIS to see if there’s a match with a known criminal offender. But if there’s no match, the perpetrator’s identity might remain unknown.

Investigative genetic genealogy marries these two fields. With it, criminal investigators can take an unknown suspect’s DNA profile and upload it to a public database to learn about the suspect’s family members. Investigators can then use the genealogical information and other evidence to build back through the family tree and identify potential suspects.

From there, investigators do general detective work to narrow down the suspect pool to one person. This can mean looking at people’s age, location, physical appearance or ability to carry out the crime.

How the method was used in this case

In the case of the Idaho student killings, the use of investigative genetic genealogy remains a bit unclear.

On Sunday, November 13, 2022, police in Moscow, Idaho, were called to a home near the University of Idaho and inside found the fatally stabbed bodies of four students: Kaylee Goncalves, Madison Mogen, Ethan Chapin and Xana Kernodle.

In the days afterward, officials said they did not have a murder weapon or a suspect. However, investigators did find a tan leather knife sheath at the scene, and the Idaho State Lab found a single source of male DNA on the button snap of the sheath, according to a probable cause affidavit.

According to the affidavit, investigators homed in on Kohberger, at the time a Ph.D student in criminology at nearby Washington State University, by using surveillance video of a vehicle in the area around the time of the killings, physical descriptions of the suspect from a surviving witness and his cell phone location data. Further, detectives took DNA from the trash at the Kohberger family’s home in Pennsylvania and compared it to the DNA on the sheath, and identified “a male as not being excluded as the biological father of Suspect Profile,” according to the affidavit. Kohberger was then arrested on December 30, 2022.

In all, investigative genetic genealogy was not mentioned in the arrest warrant or in any search warrants in the case.

However, court documents filed by prosecutors in June 2023 revealed the FBI originally loaded the DNA profile from the knife sheath onto public genealogy sites. “The FBI went to work building family trees of the genetic relatives to the suspect DNA left at the crime scene in an attempt to identify the contributor of the unknown DNA,” and then sent a tip to investigate Kohberger, according to prosecutors.

The tip “pointed law enforcement toward (the) Defendant, but it did not provide law enforcement with substantive evidence of guilt,” according to the filing.

That filing also stated prosecutors used a traditional “STR” DNA comparison, a common type of DNA profiling used in criminal cases, and found Kohberger was a “statitistical match” with the DNA from the knife.

Why the defense keeps bringing it up

The prosecution has argued investigative genetic genealogy was not mentioned or used in the warrants and will not be presented at trial, so it’s therefore not relevant to the case. However, Kohberger’s defense has argued they should be entitled to access all DNA data used in the case, including material from the FBI’s investigative genetic genealogy process, to better prepare for their defense.

Last October, Judge ruled Kohberger’s team has a right to see some of the material in preparation for his defense.

“The State’s argument that the IGG investigation is wholly irrelevant since it was not used in obtaining any warrants and will not be used at trial is well supported,” Judge wrote. “Nonetheless, Kohberger is entitled to view at least some of the IGG information in preparing his defense even if it may ultimately be found to be irrelevant.”

Judge said he would review the investigative genetic genealogy information to determine what needs to be shared and issue any necessary protective orders. In January, after that review, he ordered some of the IGG material be shared with the defense team, though he placed that material under seal.

Lynch, the general counsel of the Electronic Frontier Foundation, has written about the broader legal issues with genetic genealogy. She said the technique threatens to violate people’s 4th Amendment rights prohibiting unreasonable searches, saying people’s DNA is private.

“There’s a tendency for judges, for the public, to say, ‘Oh, well, these crimes are so terrible that it justifies any kind of search to possibly identify the person,’” she said. “But what we have to realize is that these kinds of investigative techniques are not limited to cold cases and not limited to heinous felonies. They will be used in even minor crimes, and they can implicate people for crimes they didn’t commit.”

CNN’s Taylor Romine, Veronica Miracle and Jeffrey Kopp contributed to this report.

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