(CNN)Evidence in the case of a Tennessee man who was sentenced to death three decades ago can be tested for the first time for DNA, a judge ruled this week.
Pervis Payne, who has been on death row for 32 years, is scheduled for execution in December.
He received two death sentences after he was convicted in 1988 of two counts of first-degree murder for the June 1987 stabbing deaths of 28-year-old Charisse Christopher and her 2-year-old daughter in the Memphis suburb of Millington. Payne also was convicted of assault with intent to commit first-degree murder of Christopher's 3-year-old son, who survived.
Payne, 53, maintains that he is innocent and went into Christopher's apartment after hearing a cry for help, according to court documents. He said he pulled the murder weapon, a butcher knife, from her neck, the documents say.
He is represented by The Innocence Project, a national group of attorneys and investigators that often uses new DNA evidence to exonerate their clients.
"However, in the Court's view, the Petitioner has established a reasonable probability he would not have been convicted of first degree murder had exculpatory evidence been presented to the jury," Shelby County Criminal Court Judge Paula Skahan wrote in her ruling granting Payne's motion requesting DNA analysis.
Following Wednesday's ruling, Vanessa Potkin, director of post-conviction litigation at The Innocence Project and a member of Payne's legal team, said in a statement that Skahan's decision was "thoughtful and reasoned."
"When DNA evidence exists in a death penalty case, as it does here, it should always be tested to avoid the irreversible act of executing an innocent man," she said.
The motion asks for the knife, bloody clothing, and some bloody objects from the crime scene to be DNA tested.
"We have been clear from the beginning that DNA testing can be completed within 60 days," Potkin said. "DNA testing is an important piece of the puzzle in this case, which has been racially charged from the start."
Payne, a Black man, ran from the scene, according to a police officer's testimony. According to court documents, Payne said his clothes had been bloodied when Christopher grabbed him. As police arrived, he said he left in a panic, thinking he looked guilty to the officer, who didn't believe he was not the killer.
Payne said he saw another man leave the scene before he got to the second-floor apartment.
If DNA testing finds a lack of Payne's DNA on items such as the victim's bloody clothing or it finds a third person's DNA, that could provide proof of another killer and exonerate Payne, the Innocence Project says on its website.
Shelby County District Attorney Amy Weirich said her office won't appeal the order.
"We will await the results of the testing that defense assures can be done quickly. We do however have concerns that touch DNA has been deposited on the items over the last 33 years since the murders happened," Weirich said in a statement.
Payne's request to test fingerprint evidence was denied, the judge said, because it was not covered in Tennessee's post-conviction DNA law.
In a separate motion filed in federal court, the Innocence Project argues that Payne shouldn't be on death row because he has an intellectual disability.
On September 14, attorneys for Payne filed a complaint in the US District Court for the Middle District of Tennessee to prevent his execution until Tennessee creates a procedure to adjudicate his claim that, "as a person with intellectual disability," his execution would be unconstitutional.