The man charged with murdering four University of Idaho students in 2022 pleaded guilty on Wednesday as part of a deal with prosecutors to avoid the death penalty.

Bryan Kohberger, 30, sat at a table with his legal team as he entered the plea in a Boise, Idaho, courtroom.

Kohberger killed Kaylee Goncalves, Ethan Chapin, Xana Kernodle and Madison Mogen at a rental home near campus in Moscow, Idaho, in the middle of the night in November 2022. Autopsies showed the four were all likely asleep when they were attacked, some had defensive wounds and each was stabbed multiple times.

Relatives of at least two of the victims attended Wednesday's court hearing. At least one of the victim's families was "furious" Kohberger had struck a deal to escape execution, according to their attorney.

Kohberger will be sentenced at a later date.

Then a criminal justice graduate student at Washington State University, Kohberger was arrested in Pennsylvania weeks after the killings. Investigators said they matched his DNA to genetic material recovered from a knife sheath found at the crime scene.

No motive has emerged for the killings, nor is it clear why the attacker spared two roommates who were in the home. 

Latah County prosecuting attorney Bill Thompson said Wednesday that Kohberger purchased the murder weapon with an Amazon gift card in March 2022, while he was living with his parents in Pennsylvania. That knife has not been found.

Thompson said cellphone data and surveillance video shows Kohberger visited the victims' neighbourhood at least a dozen times before the killings between July and November of that year.

The murders shocked the small farming community of about 25,000 people, which hadn't had a homicide in about five years, and prompted a massive hunt for the perpetrator.

That included an elaborate effort to track down a white sedan that was seen on surveillance cameras repeatedly driving by the rental home, to identify Kohberger as a possible suspect using genetic genealogy and to pinpoint his movements the night of the killings through cellphone data.

In a court filing, his lawyers said Kohberger was on a long drive by himself around the time the four were killed.