NEW YORK, June 21 (Reuters) - Since 2010, when Manhattan District Attorney Cyrus Vance created a unit tasked with preventing wrongful convictions, his office has received 118 post-conviction claims of innocence for possible review.

And while the program has resulted in a handful of vacated convictions, it also has informed the way that his office approaches every prosecution, he said during a speech delivered at the New York City Bar Association on Wednesday night.

"The very process of examining our procedures, of trying to articulate and to synthesize our best thinking . . . has been critical to the evolution of the conscience and culture of our office," he said. "It is now part of the way in which we transmit our values to new prosecutors in our office."

In particular, Vance said, the program has reinforced his office's commitment to pursuing cases only when prosecutors are convinced beyond a reasonable doubt that the defendant is guilty.

This standard exceeds the requirements of both state and national ethics rules, which permit prosecutors to move forward with cases if probable cause exists and rely on the jury to make a final determination.

"Put simply, if we are not convinced beyond a reasonable doubt that the defendant is guilty, how do we go into court and ask a jury of twelve to find him guilty?" he said.

That approach was on display last summer, he said, when he dismissed sexual assault charges against former International Monetary Fund chief Dominique Strauss-Kahn after having doubts about the credibility of his accuser, a hotel maid at the Sofitel Hotel in Manhattan.

TWO COMPONENTS

The Conviction Integrity Unit, which is headed by Assistant District Attorney Bonnie Sard, has two major components, Vance said.

On the "front end," assistant district attorneys apply certain guidelines to ensure that innocent people are not prosecuted. Those best practices were designed in consultation with a group of outside experts, including Barry Scheck of the Innocence Project.

They include a detailed analysis of eyewitness accounts, additional training for young prosecutors and enhanced review of the disclosure of exculpatory evidence, Vance said. In addition, complex or major cases are often discussed at "round tables" of senior assistant district attorneys.

On the "back end," the unit examines claims of innocence raised for defendants that already have been convicted.

That process, Vance said, forces the office to confront questions without easy answers, such as how much evidence should be required to vacate a conviction and whether a guilty plea should preclude re-examination.

One surprising conclusion after two years is that DNA evidence has not resolved a single claim of innocence, Vance said.

Without dispositive scientific evidence, the office must consider how to weigh a jury's verdict. Vance said the unit would vacate a conviction despite a guilty verdict if prosecutors discovered new evidence or a flaw the jury could not have been aware of.

He said the unit is "strongly disinclined," however, to overrule a jury in the absence of new evidence, even if prosecutors conclude they likely would have rendered a different verdict.

"When we exercise our power, it has to be done responsibly and, I believe, with a sense of humility," he said. "And that may require us to dismiss charges, no matter the public outrage and promise to proceed."

(Reporting by Joseph Ax)

Follow us on Twitter @ReutersLegal | Like us on Facebook