In Moscow, Idaho, Police Chief James Fry unwrapped the best holiday gift when officers named Bryan Christopher Kohberger, 28, as the alleged killer in the quadruple homicide that captured the country’s attention for weeks.

On November 13, University of Idaho students Ethan Chapin, Madison Mogen, Xana Kernodle and Kaylee Goncalves were fatally stabbed in a house near campus. For more than a month, investigators fielded more than 19,000 tips and held 150 interviews, per the Today Show. And while media regularly reported on the case, the department kept mum on most developments until the last few days of 2022. On December 30, Fry announced Kohberger was taken into custody at his parents’ home in Albrightsville, Pennsylvania. 

The Washington State University Criminal Justice and Criminology Ph.D. student waived extradition and was escorted to Idaho last month. He faces four counts of first-degree murder, as well as one felony burglary charge. An 18-page court filing explained how Moscow P.D. recovered DNA from a leather knife sheath left at the scene that matched a family member from a sample pulled out of the Kohberger’s trash with 99.9998% certainty, reported CBS News. That genetic evidence, along with details related to his vehicle and cellphone data, directed officers to Kohberger.

Of course, DNA has been a pivotal player in criminal cases for decades. Improvements in technology and science have advanced its investigative potential, including delivering results from miniscule samples. The commercialization of genetic ancestry services also supplements agencies’ genetic comparisons through extended family members instead of a single individual donor. At one point in the investigation, the New York Post wrote that detectives used private-sector genetic databases to search for the suspect. 

While that appears to have been misinformation, the method, known as investigative genetic genealogy (IGG), has empowered cops to close some very cold cases, such as the Golden State Killer case, which led to a 2018 arrest. In 2022, IGG helped police in Orange County, California, solve two cold cases dating back to the 1980s. 

“The justice that every victim deserves was hidden away in DNA, but with advances in IGG technology combined with the relentless dedication of generations of detectives and the talented prosecutors and forensic scientists at the District Attorney’s Office, we now know who killed Renee [Cuevas] and Shannon [Lloyd],” Orange County District Attorney Todd Spitzer said in a statement.

IGG enabled police in Philadelphia to finally identify a 65-year-old John Doe, who became known as the Boy in the Box. In 1957, a college student found a child’s body in a cardboard box in the woods northeast of Philadelphia. An autopsy concluded he had been beaten to death and the body abandoned. 

DNA from two exhumations of the unknown 4-year-old male allowed genealogists to identify two related individuals who sent in their samples for ancestral tracing. That connection served as the basis to construct the boy’s family tree, which narrowed down the possibilities on both maternal and paternal branches, eventually leaving Joseph Augustus Zarelli as the only genetic match. The investigation into his death is ongoing.