How police used DNA evidence to track murder suspect Bryan Kohberger

US police and the FBI used a unique method to hunt down the man they accuse of stabbing to death four Idaho University students.

Police in the US traced the alleged Idaho University mass killer through the DNA of his family members.

Investigators had DNA from an unknown person at the grisly scene of the killings

of Kaylee Goncalves, 21, Madison Mogen, 21, Xana Kernodle, 20, and Kernodle’s boyfriend Ethan Chapin, 20, who were killed in their beds at their home in Moscow, Idaho on November 13.

But there was no link to any DNA on record so they used genetic genealogy techniques to identify Bryan Christopher Kohberger, CNN reported.

The DNA was run through a public database to find potential family member matches to the 28-year-old, and inquiries led to his identification as the suspect, a law enforcement source told CNN.

Kohberger was arrested after a dramatic 3am raid that followed a nationwide manhunt by state police and the FBI, who collected thousands of pieces of evidence and more than 20,000 tips from the public.

He was arrested in mountainous Scranton, Pennsylvania more than 3,000km away.

Kohberger is reportedly a criminology student, but not at the University of Idaho the four victims attended.

He has been charged with four counts of first-degree murder and one count of burglary. The murder weapon has not been found

University of Idaho murder victims (and two housemates that survived) – Left to right – Dylan Mortensen, Kaylee Goncalves (with Madison Mogen on shoulders), Ethan Chapin, Xana Kernodle and Bethany Funke. Picture: Instagram

Two others were home at the time of the killing spree, but were uninjured.

Shocking images from the scene showed blood dripping down the side of the building, which experienced police said was one of the worst they had seen.

Police were focusing their search for a white 2011-13 Hyundai Elantra that was believed to have been in the area at the time of the murders. According to investigators, the occupant of the correct car may have “critical information” related to the case.

CNN reports his DNA was discovered at the scene of the crime and police established a link between the car and Kohberger after a white Hyundai Elantra was found at his home.

A chilling photo posted on Instagram hours before the murders showed the four roommates together, smiling, with Ms Mogen on Ms Goncalves’ shoulders.“One lucky girl to be surrounded by these people every day,” Ms Goncalves wrote.

The frenzied attacks have sparked theories about motives and suspects after weeks of headlines. Each victim was stabbed multiple times in the chest area.

Moscow Police and the University of Idaho are set to hold a press conference on Saturday morning Australian time.

Bryan Christopher Kohberger was taken into custody by police and the FBI around 3am. Friday in Scranton, Pennsylvania, according to reports. Picture: Monroe County Correctional Facilyu

Best friends Ms Goncalves and Ms Mogen, who met in the sixth grade, were last seen on surveillance footage at Moscow’s Corner Club just hours before the stabbings. They then stopped at a food truck before returning to their rented home before 2am.

Ms Kernodle and Mr Chapin had been at a party at a nearby fraternity house and had arrived home shortly before, reported the New York Post.

University of Idaho murder victims (and two housemates that survived) - Left to right - Dylan Mortensen, Xana Kernodle, Bethany Funke, Kaylee Goncalves,, Madison Mogen. Picture: Instagram

University of Idaho murders - Kaylee Goncalves and Madison Mogen seen on food truck CCTV footage taken on at about 1:41 a.m on the same day as the murders. Picture: CNN

Police say the four students were murdered sometime between 3 and 4am but they were not discovered by roommates Dylan Mortensen and Bethany Funke until much later that morning. Mr Mortensen and Ms Funke had become worried when they could not contact their friends and called police, who made the grim discovery.

Police have faced growing criticism for not making an arrest.

University of Idaho murder victims (and two housemates that survived) - Left to right - Dylan Mortensen, Kaylee Goncalves, Bethany Funke, Madison Mogen and Xana Kernodle. Picture: Instagram

Moscow Police Department Chief James Fry previously told media any information was useful to his department and urged people to come forward because “your information might be one of the puzzle pieces that help solve these murders”.

- with The New York Post

Originally published as How police used DNA evidence to track murder suspect Bryan Kohberger