Court: Man freed from Ohio death row after 2 decades can't be retried A man held for more than 21 years on Ohio's death row - whose conviction was thrown out by a federal judge after ruling that prosecutors withheld potentially exculpatory evidence -- cannot be tried again in the case, the U.S. Supreme Court has ruled. The state had wanted the court to review a ruling last August by the U.S. Circuit Court of Appeals in favor of former inmate Joe D'Ambrosio, according to The Associated Press. D'Ambrosio was convicted of murder in the death of Tony Klann, 19, whose body was found in a Cleveland creek in 1988. A federal judge ruled in 2006 that prosecutors had not turned over evidence that could have led a panel to find him not guilty and threw out his conviction. D'Ambrosio was freed in 2009, the same federal judge barred his re-prosecution in 2010 and a county judge dismissed the charges against him in 2011, according to The Plain Dealer. "Today was 23 years in the making," D'Ambrosio said in a statement. Justice has finally prevailed. D'Ambrosio is the 140th former death row inmate to be exonerated since 1973 and the sixth from Ohio, according to the Death Penalty Information Center. "What this case clearly shows is that the death penalty system in Ohio with all of its safeguards still makes mistakes and I think we're just relieved that Joe D'Ambrosio had some extraordinary attorneys who worked tirelessly for ... 20, 30 years to prove that he was not guilty," Kevin Werner, executive director of Ohioans to Stop Execution, told msnbc.com. "This is a moment that really should give Ohio officials pause because right now they're fighting over the lethal injection process and how those rules are or are not followed at the same time that the state Supreme Court has commissioned a task force to assess how fair and accurate is the death penalty system, and I think Joe D'Ambrosio's case is a pretty clear indication that the death penalty system is not working," he added. The number of death sentences imposed in the U.S. has taken an "historic drop" -- about 75 percent -- over the last 15 years, accompanied by a nearly 60 percent decline in the number of executions, the Death Penalty Information Center said in its annual report in December. Recent polls showing a withering of support for capital punishment over controversial cases like that of Troy Davis, who was executed in Georgia in September. The decline in the use of the death penalty also has likely been influenced by states" worsening financial conditions, said Richard Dieter, the center's executive director. Msnbc.com's Miranda Leitsinger and The Associated Press contributed to this report.