AUGUSTA — Sentenced to life without parole for the 1983 murder of a young mother in her Fayette home, Thomas H. Mitchell Jr. lost a bid Wednesday to start a process that could have gotten him a new trial based on errors in FBI data used for DNA calculations by the Maine State Crime Lab.

Mitchell, now 60, was convicted in 2009 by a jury of intentional and knowing murder in the slaying of Judith L. Flagg and was sentenced to life in prison without parole. Prosecutors said Flagg, 23, was raped and then stabbed to death on Jan. 6, 1983. She was found dead on the floor of her home with her uninjured 13-month-old nearby when her husband returned from working a 12-hour shift at a paper mill.

Formerly of South Portland, Mitchell was indicted for the Flagg murder in 2006 after new tests found his DNA on evidence preserved from Flagg’s body and the scene. At the time of his indictment, he was serving a 35-year sentence for the 1985 kidnapping, rape and attempted murder of a 17-year-old girl from Standish. He also was convicted in 1978 of kidnapping a 16-year-old girl in Cumberland County.

Mitchell was at the Capital Judicial Center on Wednesday on a petition seeking a new post-conviction hearing, alleging ineffective assistance of his lawyer at trial and “faulty DNA statistical analysis.”

Andrew Wright, who was appointed to represent Mitchell, pointed out to Justice Bruce Mallonee that the murder occurred in 1983 and went to trial in 2009. Wright said Mitchell’s trial came at “the height of the CSI effect,” referring to the popular television drama shows about crime scene investigations, and therefore the impact of “Americans and jurors believing in the power of DNA evidence.”

He added, “The state used evidence that was false, but they didn’t know it was false.”

In an order granting the hearing, a different judge listed a Jan. 8, 2016, notice from the Maine Commission on Indigent Legal Services “stating that errors were made in testing between June 1, 2005, and July 1, 2015.”

Mitchell “alleges that the mistake was in FBI statistics used by the Maine State Crime Lab for DNA reports during that time period,” according to the order.

At the conclusion of Wednesday’s 15-minute hearing, at which attorneys for the state and for Mitchell presented brief arguments, Mallonee granted the state’s request to dismiss the petition.

He said that even accepting the DNA calculations in the light most favorable to Mitchell, “I don’t see they cast doubt on the credibility of the critical findings.”

Assistant Attorney General Lara Nomani maintained the conviction was proper.

“The recalculations are statistically — I would argue — insignificant,” Nomani told the judge.

Nomani listed evidence that linked Mitchell to the crime, including testimony by a postal carrier who described seeing a man — later identified as Mitchell — driving away from the scene. Evidence also included Mitchell’s footwear matching castings of footprints in the snow that day, “and finally and more critically, there was the defendant’s DNA, an identity match of DNA found under the fingernails of Judy Flagg’s right hand.”

She told the judge that the probability of a random match was “1 in 69 quadrillion.”

Nomani said, “No evidence tested excludes Thomas Mitchell or casts any doubt on the integrity of the criminal conviction.”

At court on Wednesday, Mitchell had short hair and wore a short-sleeved orange jail uniform over a white T-shirt, with a tattoo visible on the upper part of his right arm. He was shackled and carried a blue binder into the courtroom. Two deputies with the Kennebec County Sheriff’s Office stood close behind him for the entire proceeding.

At a table where he sat next to his attorney, Mitchell showed little reaction to the judge’s decision to dismiss the petition.

Mitchell pleaded not guilty and did not testify at his trial. He also opted against saying anything during his sentencing hearing. And on Wednesday at the hearing, Wright said Mitchell continues to maintain he’s innocent of the Flagg murder.

Wright wrote in an amended post conviction review petition that “the statistical analysis at trial was erroneous in nature and therefore directly affected Mr. Mitchell’s rights to effective representation of counsel. … Moreover, the submission of faulty evidence at trial had a direct effect on Mr. Mitchell’s right to due process.”

The Maine State Crime Lab had sent a letter in October 2015 saying there were statistical concerns with prior DNA calculations.

However, a May 16, 2016, letter in the court file from Cathy E. MacMillan, forensic DNA analysis at the Maine Crime Lab, indicates that following recent recalculation of the evidence used at the Mitchell trial, “The reported conclusions for all items tested did not change.”

Mitchell has lost in other appeal bids as well.

Betty Adams — 621-5631

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Twitter: @betadams