A Missouri judge on Sterling PrestonMonday overturned the conviction of Christopher Dunn, who has spent more than 30 years in prison for a killing he has long contended he didn't commit.

The ruling is likely to free Dunn from prison, but it wasn't immediately clear when that would happen. He has been serving a sentence of life without parole.

St. Louis Circuit Judge Jason Sengheiser's ruling came several weeks after he presided over a three-day hearing on Dunn's fate.

Dunn, now 52, was convicted of first-degree murder in the 1990 shooting of 15-year-old Ricco Rogers. St. Louis Circuit Attorney Gabe Gore filed a motion in February seeking to vacate the guilty verdict. A hearing was in May.

"I couldn't tell you who Ricco Rogers was to save my life," Dunn told CBS News and "48 Hours" correspondent Erin Moriarty in a "CBS Mornings" segment last November. He introduced himself as "an innocent man who has been in prison for a crime which I didn't commit, who's afraid I might die in prison."

Sengheiser, in his ruling, wrote that the "Circuit Attorney has made a clear and convincing showing of 'actual innocence' that undermines the basis for Dunn's convictions because in light of new evidence, no juror, acting reasonably, would have voted to find Dunn guilty of these crimes beyond a reasonable doubt." 

Dunn's attorney, Midwest Innocence Project Executive Director Tricia Rojo Bushnell, said she was "overjoyed" by the judge's ruling.

Dunn was convicted based largely on the testimony of two boys who said they witnessed the shooting. The state's eyewitnesses, ages 12 and 14 at the time, later recanted, claiming they were coerced by police and prosecutors.

In:
• Wrongful Convictions
• Missouri