An Oregon man arrested and convicted of manslaughter years after the 2000 death of his 15-year-old girlfriend is expected to walk out of prison late Tuesday after the state decided not to appeal a recent ruling that overturned the conviction.

Coos County District Attorney Paul Frasier said lawyers for the state told him they wouldn’t appeal the ruling. Frasier also decided against a new trial for Nicholas McGuffin, 37, in the death of Leah Freeman.

A judge earlier this month overturned McGuffin’s conviction because the Oregon State Police crime lab failed to disclose that it had found another man’s DNA on the girl’s shoe. Malheur County Circuit Senior Judge Patricia Sullivan concluded that the crucial DNA information could have led the jury to acquit McGuffin.

Frasier said he thinks authorities convicted the right man, but the passage of time and concerns with witnesses’ memories and availability made a new trial a challenge. He said given the large volume of records in the case, he doubted he would be able to prepare for a trial before McGuffin’s scheduled release next August.

He said Cory Courtright, Freeman’s mother, opposed another trial. Her view was a major consideration, the district attorney said.

“She does not want to go through the pain and stress of another trial,” Frasier said. “She does not want us to pursue a new trial.”

The DA’s decision means McGuffin leaves prison with a clean record. He had been held at South Fork Forest Camp, a minimum-security work camp east of Tillamook. He served nine years of a 10-year sentence.

“He is walking out of prison innocent, with no convictions, after nine years of being wrongfully convicted and in prison,” said Aliza Kaplan, a professor at Lewis & Clark Law School and director of the school’s Criminal Justice Reform Clinic. “He has has maintained his innocence from the beginning and he will get to reunite with his family and be with his daughter.”

McGuffin’s release represents a major victory for the Forensic Justice Project, a small nonprofit supported by state money and grants. The organization’s mission is preventing and identifying wrongful convictions based on flawed forensic science. Oregon is one of a handful of states to fund such efforts.

Freeman vanished June 28, 2000, after leaving a friend’s house. One of her shoes was found by a cemetery in town that night; the other about a week later off a rural road. Her body was found five weeks later down a steep embankment. It was so badly decomposed, the medical examiner could not determine how she died.

Her boyfriend at the time was McGuffin. Then 18, McGuffin was investigated for the crime, but the case eventually went cold. No physical evidence linked McGuffin to the crime.

In 2008, local police put together a team of detectives to reinvestigate the case. They identified a dozen suspects, including McGuffin.

Two years later, Frasier took the case to grand jury and sought an indictment against McGuffin.

In 2011, a jury fund him guilty of manslaughter in a 10-2 verdict.

Noelle Crombie; ncrombie@oregonian.com; 503-276-7184; @noellecrombie

Subscribe to Oregonian/OregonLive newsletters and podcasts for the latest news and top stories.