California Gov. Jerry Brown ordered new DNA tests that a condemned inmate says could clear him in a 35-year-old quadruple murder case that's drawn national attention. Brown ordered tests Monday of four pieces of evidence that Kevin Cooper and his attorneys say will show he was framed for the 1983 Chino Hills hatchet and knife killings of four people.

The items that will be tested are a tan T-shirt and orange towel found near the scene and the hatchet handle and sheath.

Cooper was convicted in 1985 of killing Doug and Peggy Ryen, their 10-year-old daughter Jessica and 11-year-old neighbor Christopher Hughes. Prosecutors say Cooper's claims of innocence have been disproven multiple times, including by prior DNA testing, but Cooper and his attorney argue evidence against him was planted.

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"I take no position as to Mr. Cooper's guilt or innocence at this time, but colorable factual questions have been raised about whether advances in DNA technology warrant limited retesting of certain physical evidence in this case," Brown wrote in his executive order.

Brown also appointed a retired Los Angeles County Superior Court judge to serve as a special master overseeing the case.

New York Times columnist Nicholas Kristof, U.S. Sen. Kamala Harris, state Treasurer John Chiang and reality television star Kim Kardashian are among people who called for Brown to order new DNA tests.

Wonderful Christmas news: Gov Brown has ordered DNA testing in the case of Kevin Cooper, whom I believe was framed for a quadruple murder. After several decades, we may finally learn definitively what happened. Congrats to Cooper, his legal team, and all who fought for testing. — Nicholas Kristof (@NickKristof) December 24, 2018

Just saw the press release from Governor Brown regarding Kevin Cooper! Such amazing news! pic.twitter.com/GUVIgcQYDq — Kim Kardashian West (@KimKardashian) December 25, 2018

Brown's Christmas Eve order came alongside 143 pardons and 131 commutations, in keeping with his tradition of granting clemency on or near major holidays.

In the Cooper case, the purpose of the new testing is to determine whether DNA of any other identifiable suspect is on the items. If the tests reveal no new DNA or some that cannot be traced to a person, "this matter should be closed," Brown wrote.

Two previous tests showed Cooper, 60, was the killer, argued San Bernardino County District Attorney Mike Ramos. He previously said the tests proved Cooper had been in the Ryens' home, smoked cigarettes in their stolen station wagon, and that Cooper's blood and the blood of at least one victim was on a T-shirt found by the side of a road leading away from the murders.

Cooper's attorney, Norman Hile, said his client's blood was planted on the T-shirt, and that more sensitive DNA testing would show who wore it. He contends investigators also planted other evidence to frame his client, a young black man who escaped from a nearby prison east of Los Angeles two days before the murders.

Neither Ramos nor Hile could be reached for comment Monday.

CBS News correspondent Erin Moriarty -- who's covered the case for some 20 years -- reports there was evidence pointing to another suspect and in testimony at trial it was learned that a sheriff's deputy destroyed it.

When Diana Roper, now deceased, found bloody overalls belonging to her boyfriend, a man with a violent criminal history, she turned them in.

"Wouldn't you say that taking in coveralls that appear to be covered in blood, not sending them to a lab and throwing them away before trial would be highly unusual?" Moriarty asked Floyd Tidwell, who was the sheriff at the time.

"I don't know that that happened," Tidwell said. "I'm very vague on that."

Other evidence points to the killers being white or Hispanic, Cooper's supporters say. A San Diego judge in 2011 blocked Cooper's request for a third round of DNA testing.

Cooper's scheduled execution in 2004 was stayed when a federal appellate court in San Francisco called for further review of the scientific evidence, but his appeals have been rejected by both the California and U.S. supreme courts. Former Gov. Arnold Schwarzenegger twice denied Cooper's clemency petitions.

California hasn't executed anyone since 2006.