(CNN) — It was something former New York Supreme Court Judge Frank Barbaro just couldn’t get out of his mind: His 1999 second-degree murder conviction of a white man who said he killed a black man in self-defense.

On Thursday, 15 years after that conviction, a new judge is expected to announce her decision either to overturn the murder conviction or let Barbaro’s decision stand.

The case is being revisited because Barbaro, a white judge who had gained a reputation as a staunch supporter of civil rights, says his own racial bias may have led him to convict the suspect of murder.

“I couldn’t get out of my mind the look on the lawyer’s face when I said I found him guilty. And the defendant on the stand, like he was pleading to me, ‘It just happened, it just happened,’ and that was sort of haunting me,” Barbaro said earlier this year in an exclusive interview with CNN.

The defendant was Donald Kagan, now 39, who was charged with the murder of Wavell Wint, 23, after shooting him during a confrontation at a Brooklyn movie theater in 1998.

Kagan, who is white, testified during a two-day trial before Barbaro that during the confrontation he had been afraid of Wint, who was black.

Kagan said he came to the theater armed because the neighborhood had a reputation of being unsafe.

Wint, according to the trial record, had been confrontational with a number of people that night before the encounter with Kagan. Wint was not armed.

When their paths eventually crossed, words were exchanged and they scuffled. Wint was shot and killed, and Kagan was charged with murder. Barbaro landed the bench trial.

Barbaro said it may have been because of his reputation for fairness that Kagan chose to put his fate in the judge’s hands and not a jury’s.

In his opinion, Barbaro wrote, “The circumstantial evidence convinces the court that when [Kagan], in response to [Wint’s] verbal taunts, pulled out his gun for the second and last time, he fully intended to kill [Wint].”

He said later that he did not give much weight to the self-defense argument presented by Kagan’s attorney. He was convinced at the time that Kagan was racist and wanted to kill a black person, he said.

Barbaro found Kagan guilty of second-degree murder and criminal possession of a weapon. He was sentenced to 15 years to life in prison, where he remains today.

‘I think I made a mistake’

Several years after the Kagan verdict, Barbaro wondered if he may have been wrong to convict him of murder.

Barbaro always had his pulse on the cause of civil rights. He stuck up for the underdog in his personal life and professionally, as a lawyer and former state legislator, before becoming a judge.

Was he so influenced by his civil rights passions that he had assumed the only reason Kagan shot Wint was because Wint was black? Had he given Kagan a fair trial?

Patti Barbaro, the judge’s wife, told CNN earlier this year, “He said, ‘I really feel I need to revisit this case. I need to get the transcripts. I don’t feel comfortable with this. It’s been haunting me.'”

Finally, in 2011, Barbaro called Kagan’s defense attorney Jeff Adler and made an amazing admission:

“I think I made a mistake,” he told him. He asked the attorney to send him the transcript of the trial.

After reading his own trial record, Barbaro came to the conclusion that in his quest for equality between the races, he completely ignored the trial evidence that had to do with Kagan’s claim of self-defense. He realized he really hadn’t considered whether Kagan felt an imminent fear for his life during the confrontation.

That began the process of a lengthy new legal battle, with the defense filing a motion to set aside Barbaro’s murder verdict based on one of the most unusual claims the courts would ever hear: The trial judge was admitting he had not given the defendant a fair trial.

The judge — who by then had retired and no longer had jurisdiction in the case — became, in effect, a witness for the defense of the man he had convicted years earlier.

Wint’s family: ‘It’s not fair’

Barbaro testified at a December 2013 hearing and was cross-examined by the prosecution, who questioned the judge’s memory of events in an effort to discount his admission of racial bias.

The family of Wavell Wint, including his now-grown son, attended that hearing, too. They were angry that the justice they felt they received with the verdict so many years ago could possibly be taken away.

One month later, Wint’s family returned to court to hear arguments on the issue by both sides. In an impassioned plea, the prosecution told the court the conviction should stand, that 14 years ago Judge Frank Barbaro thoughtfully issued a very well-reasoned opinion. They said even if his personal beliefs colored his perception of the case, that was not grounds to overturn the verdict.

“It’s not fair,” said Carmen De Jesus, who was Wint’s girlfriend and the mother of his child. “My son grew up without a father, it’s not fair. [Kagan] pulled out the gun and he murdered that man.” Wint’s family told CNN.

Judge ShawnDya L. Simpson, who presided at the December hearing, is expected to issue a decision Thursday. Simpson has postponed giving her decision in this case two times already this year. Those close to the case say there is a possibility she may postpone again.

Even if Barbaro’s verdict stands, Kagan still is eligible for parole this fall.

“It wasn’t difficult to come forward,” Barbaro said after testifying in a hearing on whether Kagan should be freed. “It is painful to know I sent an innocent man to jail.”