PORTLAND, Maine — The Maine Supreme Judicial Court on Tuesday sent murderer Jeffrey Cookson’s request for DNA testing of clothes and a wig allegedly worn by an alternative suspect back to Penobscot County Superior Court on procedural grounds.

Cookson, 47, is serving consecutive life sentences at the Maine State Prison for the slaying in December 1999 of his ex-girlfriend Mindy Gould, 20, and the boy she was baby-sitting, Treven Cunningham, 21 months old, both of Dexter.

In a 5-1 decision, justices found that Maine Superior Court Justice Roland Cole should have issued written findings of fact as to why the evidence Cookson asked to be tested in 2009 did not meet criteria outlined in state law.

The state supreme court also ruled Tuesday that Cookson has the burden of proving that proper procedures were followed to maintain the required chain of custody of the evidence he wants tested.

Justices heard arguments in the appeal in January in Portland.

“This is a victory for Mr. Cookson,” Karen Wolfram, the Portland attorney who represented him in the appeal, said Tuesday. “He is a step closer to having the evidence tested and a new trial.”

Wolfram did not represent Cookson at his trial.

Deputy Attorney General William Stokes, who heads the criminal division of the Maine Attorney General’s Office, called the decision “fairly narrow.”

Justices Jon Levy, Warren Silver, Ellen Gorman and Joseph Jabar joined Chief Justice Leigh I. Saufley in the majority. Justice Donald Alexander dissented.

Justice Andrew Mead recused himself.

Cookson continues to maintain his innocence.

He was convicted in December 2001 by a Penobscot County jury of shooting the two execution-style on Dec. 3, 1999, at the Dexter home of Gould’s sister. A few days before her death, Gould had taken out a protection from abuse order against Cookson, then of Dover-Foxcroft, according to previously published reports.

The appeal justices ruled on Tuesday dealt with information given to Cookson’s trial defense attorney, William Maselli of Auburn, but not shared with law enforcement officials or Justice Cole, who presided at Cookson’s trial, until shortly after the verdict was announced. In 2001, Maselli said that David Vantol, then 21 and living in Guilford, had admitted to him that he committed the murders.

Vantol later led investigators to the murder weapon, which until then had not been found, and the clothes and wig he said he had been wearing when he killed the boy and Gould, the briefs in the current appeal agreed. Vantol repeatedly told police in December 2001 that he committed the crimes at Cookson’s request and an offer of $10,000.

Two months later, at a hearing on Maselli’s motion for a new trial, Vantol, who was described in court as a man with a history of mental illness and a limited education, recanted his confession. Records showed that Vantol visited Cookson in jail in 2001. Investigators and prosecutors speculated in 2002 that that was how Vantol learned the details of the murders.

The Maine Supreme Judicial Court in December 2003 unanimously affirmed Cookson’s convictions and sentences. Justices unanimously found that Maselli’s decision not to tell police or the judge that Vantol had confessed to the crimes was a “tactical” decision by the defense team.