Judge Jeanine says that her source told her that the suspect in the Idaho murders was caught via genealogical dna tracing. This makes sense, since apparently the perpetrator had no criminal record and his dna would not be in any law enforcement database.

How does it work? This is how they caught the Golden State killer. The police had dna evidence from some of the crime scenes, but the criminal’s dna was not in any law enforcement database, which meant that the criminal had probably never been arrested.

Recently, because many of us have submitted our dna to databases as we search our own genealogical records, genealogists have been able to match criminal dna to the profiles already in genealogy databases. In this way, they are sometimes able to find close relatives of the criminal and narrow the possible suspects to just a few. That is what happened with the Golden State killer.

L.A. Times

The dramatic arrest in 2018 of Joseph James DeAngelo Jr. was all the more astounding because of how detectives said they caught the elusive Golden State Killer — by harnessing genetic technology already in use by millions of consumers to trace their family trees.

[. . .]

Investigators and prosecutors said the investigation relied on genetic information people voluntarily made public, though with little reason to suspect it might incriminate members of their families in crimes. The actual investigation was broader and more invasive, conducted without a warrant, and appeared to violate the privacy policy of at least one DNA company.

When DeAngelo was arrested, prosecutors would say only that they had used family tree searches to find relatives of the killer and, from there, identified DeAngelo. Shortly after, a detective confirmed the investigative team had uploaded semen from a rape kit to develop a fresh DNA profile that was then uploaded to GEDmatch, an open-source platform frequently used by members of the public to trace their heritage.

What prosecutors did not disclose is that genetic material from the rape kit was first sent to FamilyTreeDNA, which created a DNA profile and allowed law enforcement to set up a fake account to search for matching customers. When that produced only distant leads, a civilian geneticist working with investigators uploaded the forensic profile to MyHeritage. It was the MyHeritage search that identified the close relative who helped break the case.

[. . .]

DeAngelo, 75, pleaded guilty before going to trial. He is serving 26 life sentences in a California prison. And the legality of investigative genealogy, still relatively new, has not faced serious legal challenges. It is perceived in law enforcement circles as a vital tool for solving even current crimes, but regulations and legislation have not yet caught up.

If you are interested in the details of his crimes, and how he was eventually caught, this is a good source, I think: