A California man who spent 14 years in prison after being wrongly convicted of the killing of his roommate has been exonerated and freed after prosecutors found new DNA evidence that led to a new suspect.

Key points: Ricky Davis's murder conviction is thrown out of court after DNA evidence pointed to a new suspect

Ricky Davis's murder conviction is thrown out of court after DNA evidence pointed to a new suspect The case is the second in the US where investigative genetic genealogy has led to an exoneration

The case is the second in the US where investigative genetic genealogy has led to an exoneration Another suspect has been arrested over the murder

The case is only the second in the United States — and the first in California — where investigative genetic genealogy has led to an exoneration of a person imprisoned for a crime they did not commit.

Ricky Davis's murder conviction was thrown out during a court hearing in Placerville, California, about 72 kilometres east of Sacramento.

He was later greeted by friends and family after being released from custody.

Mr Davis, 54, was convicted in 2005 of second-degree murder in the stabbing death of Jane Hylton, a 54-year-old magazine columnist.

Sacramento County district attorney Anne Marie Schubert attributed Mr Davis' exoneration, and the arrest of a new suspect, to the use of genetic and genealogical science.

Investigative genetic genealogy involves police taking crime scene DNA to genetics companies and searching for possible matches with extended family members, rather than just in criminal databases.

This allows investigators to narrow down who may have been in contact with the victim.

"It needs to be made very clear that without investigative genetic genealogy we would not be here today," she said.

"This is the first case in California and only the second in this country where investigative genetic genealogy has not only led to the freeing of an individual from prison for a crime he did not commit but the identification of the true source and as we now know the arrest of the person that did have that DNA.

"It freed Ricky Davis, it identified the other person."

Ricky Davis had always maintained his innocence. ( AP: Rich Pedroncelli )

CNN reported that the new suspect has been arrested in Roseville, California, but he could not be identified because he was a juvenile at the time of the murder.

Ms Schubert's office has been a leading force in the use of DNA evidence to crack cold cases, techniques that in 2018 led to the arrests of James DeAngelo, a suspect in the Golden State Killer/East Area Rapist case, and Roy Waller, who has been ordered to stand trial in the NorCal Rapist case.

DNA evidence points to new suspect

Ms Hylton was found dead on July 7, 1985, inside an El Dorado Hills home, which she lived in with her teenage daughter, Mr Davis and Mr Davis' then-girlfriend Connie Dahl.

Prosecutors said genetic genealogy helped investigators to determine the DNA belongs to one of the teenage boys Ms Hylton's daughter testified she was with in a park the night of the murder.

Mr Davis and Ms Dahl told detectives they had gone to a party the night before and returned home at 3:30am where they found Ms Hylton's daughter waiting outside.

Ricky Davis's murder conviction was overturned last year and he had been awaiting a new trial. ( AP: Pedroncelli )

The teenager told them she had gone out with a group of boys that night and was afraid her mother would be upset with her for being out too late, according to an online synopsis of the case by the Innocence Project.

The case went unsolved until detectives reopened it in late 1999.

DNA test results revealed an unknown male DNA profile on the nightgown in the area of a bite mark and a consistent male DNA profile under the victim's fingernails.

The test results excluded Mr Davis, Ms Dahl and Ms Hylton's daughter as the sources of the DNA, the project said.

That led to the murder conviction being overturned in 2019 after project lawyers argued that "had the original jury heard the DNA results, it would have likely reached a different outcome," the project's synopsis says.

Mr Davis had been in custody awaiting a new trial set for April.

He had always maintained his innocence.

El Dorado County district attorney Vern Pierson said he told Mr Davis that the technology which exonerated him did not exist up until recently when Mr Davis referenced how long he had been in jail.

"And I had to tell him, in all candour, if this investigation had moved forward years ago the technology did not exist, the techniques did not exist that were employed in this case to unwind it the way that we were able to do it now," he said.

"So, I wish it had occurred sooner and we could have gotten him out of custody sooner and identified, but the practical reality is it's only been in the last, really, year and a half — two years — that the genetic genealogy to identify somebody under these circumstances has been in existence."

AP/ ABC