SAN QUENTIN (CBS SF) — Gov. Jerry Brown Monday ordered further forensic tests on evidence used to convict death row inmate Kevin Cooper of the murders of a Southern California family in the 1980s.

Cooper, who has exhausted his appeals through the court system, was twice denied clemency pleas by former Gov. Arnold Schwarzenegger.

DNA evidence linked Cooper to the crime, but his attorneys have claimed the evidence in the case was tampered with, destroyed, and hidden in order to frame him.

In his order Monday, Brown ordered limited retesting of four pieces of evidence in the case using the latest advances in DNA technology.

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

The governor ordered new tests on:

  • The tan t-shirt that allegedly had Cooper’s blood on it
  • An orange towel
  • The hatchet handle of the murder weapon
  • The hatchet sheath

Brown also appointed retired Los Angeles County Superior Court Judge Daniel Pratt to oversee the process as a special master.

Cooper was convicted and sentenced to death by a San Bernardino County jury of entering the Chico Hills home of Douglas and Perry Ryen and killing the couple and their 10-year-old daughter and 11-year-old family friend.

They were found by the family friend’s father hacked and slashed to death. The victims had been stabbed a total of 143 times with an ice pick, an ax and a knife.

The couple’s eight-year-old son, whose throat was slashed, survived.

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.