(NewsNation) — Bryan Kohberger, the suspect in the Idaho college killings, is behind bars after DNA from the crime scene was linked to DNA from trash at his parent’s home. But how do investigators use genetic evidence to find a suspect?

Investigators say the key, in this case, was a sample of DNA from the crime scene being compared to the trash at the Kohberger’s Pennsylvania home. They used DNA belonging to Kohberger’s father to show a familial link, which led to Kohberger’s arrest.

Genetic genealogist CeCe Moore told News 2’s sister station, NewsNation, she thinks there’s probably more to the story than that, but it’s likely investigative genealogy played a role.

“They don’t have to include everything in the affidavit and genetic genealogy should not be used for the basis of an arrest,” Moore said.

It can be used to vet tips, like the one about the white car seen near the crime scene, she said. Police would have taken trash from the Kohberger home and used DNA from that to essentially perform a paternity test against DNA taken from the knife sheath found at the crime scene.

Kohberger is accused of killing four Idaho college students, Kaylee Goncalves, Madison Mogen, Xana Kernodle and Ethan Chapin. All four were stabbed as they slept and as weeks went by with no suspect, speculation and rumors ran rampant online.

The first break in the case came as police began searching for a white Hyundai Elantra. That car, along with forensic evidence, led to Kohberger’s arrest.

Moore said technology has increased in sensitivity over the years, allowing investigators to recover DNA even in the absence of blood. Kohberger’s DNA could have been left at the scene in a number of ways, she said, including shed skin cells or hair.

“We know from the witness statement that at least his eyebrows were showing, and it sounds like his hair wasn’t even covered. So he may have left hair behind as well, which also contains DNA,” she said.

While an arrest has been made, Moore said the search for forensic evidence isn’t over as both prosecution and defense teams will be scouring the crime scene evidence for information that can be used in court.

“There’s been a lot of work on that crime scene already, gathering any possible physical evidence to the prosecution’s case, try to support their case, or in the defense’s case, to try to find somebody else’s DNA that they can try to pin this crime on,” Moore said.