(CNN)Lamar Johnson will soon enter his 25th year behind bars.
The St. Louis man has spent more than half his life in prison for a murder the city's chief prosecutor says he did not commit.
Johnson, 45, is serving a sentence of life without the possibility of parole in Missouri. But a report from St. Louis Circuit Attorney Kimberly Gardner and the Conviction Integrity Unit outlined what her office called misconduct by police and prosecutors in the case, including perjury, false testimony and the payment of more than $4,000 to the sole eyewitness. The witness later recanted.
Dwight Warren, the assistant circuit attorney who prosecuted the case, vehemently denied the "outlandish" accusations laid out in the report, particularly the charge of paying a key witness. He also defended the detectives on the case.
"Anybody who knows me, knows that that is not my character," Warren, who was also a St. Louis police officer, told CNN. "I could probably have every judge in this circuit ... in my day testify to that. I think it's a one-sided hatchet job."
"The witness may have been compensated out of fear for his life and we may have relocated him, but this was 25 years ago and I cannot tell you with certainty," he added.
Gardner's office said it will appeal a state court judge's denial of a new trial.
Circuit Judge Elizabeth Hogan ruled last week that the court had no authority to grant a new trial because the motion was "filed approximately twenty-four years" after the mandated deadline of 15 days after the verdict.
"The evidence is overwhelming," Johnson's attorney, Lindsay Runnels, who -- along with the Midwest Innocence Project -- also plans to appeal the ruling, said via email. "The State agrees. In the interests of justice and fairness, that should be enough to overcome a missed deadline."
Two other men later signed sworn affidavits admitting to the killing
Johnson was convicted in 1995 of the murder of Marcus Boyd, who was shot to death a year earlier on the front porch of his apartment by two masked men.
Police said at the time that Johnson and another man, Phillip Campbell, fatally shot Boyd following what witnesses suggested was a drug dispute.
But Campbell and a man named James Howard later signed sworn affidavits admitting they killed Boyd and that Johnson was not involved, according to court documents.
Campbell, who died recently, was sentenced to seven years for his role in Boyd's death, according to Runnels. He served less than six years, she said. Howard is serving a life sentence for a homicide committed after Boyd's murder, she said.
"There is no statute of limitations on innocence and there is no expiration date on justice," Runnels said. "A prosecutor's duty to correct errors of this magnitude is never terminated, and rightfully so. The integrity of the justice system depends on those in power telling the truth and correcting errors when they become known."
The St. Louis Metropolitan Police Department, through a spokeswoman, declined comment.
Lone eyewitness to killing recanted his identification of Johnson
A July report by the Conviction Integrity Unit in Gardner's office cited numerous errors and examples of misconduct by police and prosecutors that deprived Johnson of a fair trial. Conviction integrity units have been created in various US cities to review post-conviction claims of innocence and exonerate wrongfully convicted defendants.
"Johnson's case is ultimately about innocence," the report said. "Johnson did not shoot Boyd and had nothing to do with Boyd's murder, and he should not be in prison for the crime. Imprisonment of an innocent person constitutes a 'manifest injustice.'"