AUBURN — A Sabattus man convicted of murder in the 2005 fatal shooting of his ex-girlfriend at his home is seeking a new trial.

Daniel Roberts, 49, has filed a motion in Androscoggin County Superior Court alleging that new DNA extraction techniques show that 29-year-old Melissa Mendoza may have handled the .38-caliber revolver Roberts claimed she was holding when he shot her in self-defense.

At Roberts’ three-week trial in 2007, prosecutors presented an expert who testified that Mendoza had been excluded as a potential donor from any traces of DNA found on the gun.

But, in a 20-page motion filed by Boston lawyer Rosemary Scapicchio and Lewiston attorney Verne Paradie, DNA testing “has made significant strides in regard to the quality of DNA testing available including, but not limited to, the sensitivity of the DNA amplification kits and an increased number of loci included in the kits.”

The defense attorneys wrote that the results of the state’s testing at the time of the trial and recent testing by a Utah human genomics DNA forensic laboratory “reveals that the testimony at trial was not accurate.”

The butt of the revolver had a “mixture of three contributors and Mendoza cannot be excluded from the two minor contributors,” the motion reads. “And the trigger had a mixture of two contributors and Mendoza cannot be excluded from the sample.”

Roberts had told police that he touched the gun at some point, given that he owned it. He said Mendoza had stolen the gun from him and entered his garage armed with it. After he shot her, the first responding officer had moved the gun before police photographed the scene, according to the motion.

“With this new testing, Roberts is able to demonstrate by clear and convincing evidence, taking the evidence at trial, coupled with the newly discovered evidence, that he meets the requirements under (state law) that he is entitled to a new trial,” the motion reads.

Roberts shot Mendoza of California in his garage shortly before 1:30 a.m. on Aug. 15, 2005. The couple had been embroiled in a custody dispute over their daughter, Savanna, 2 years old at the time of the shooting.

Roberts claimed the shooting was self-defense. But a jury agreed with prosecutors, who said Roberts had lain in wait for Mendoza, then planted the .38-caliber revolver.

Roberts was sentenced to 55 years in prison.

He had unsuccessfully appealed his conviction and later petitioned the court, claiming his constitutional rights had been violated, also appealing that decision to the Maine Supreme Judicial Court. Both times, the high court upheld the lower court’s ruling.

Prosecutors will have a chance to respond to the motion before it’s scheduled for a court hearing.