FIVE TIMES in the last five years, the U.S. Attorney’s Office in Washington has admitted to mistakes that resulted in wrongful convictions. Prosecutors can’t give back to these five men the years of their lives spent in prison for crimes they didn’t commit; that injustice is irrevocable.

But prosecutors can learn from these mistakes. So it is a promising development that a special unit is being established to determine whether others have been similarly wronged. Equally important is the unit’s mission to come up with recommendations to fix the problems that cause wrongful convictions so as to prevent future miscarriages of justice.

U.S. Attorney Ronald C. Machen Jr. announced Sept. 11 the creation of a conviction integrity unit within his office that will identify and investigate cases in which there may have been wrongful convictions and recommend practices for police and prosecutors to avoid future errors. The unit, the first for a U.S. attorney’s office, is intended not to replace the scrutiny of convictions through traditional litigation in the courts but rather to create a structure in which there is collaboration between defense and prosecutors. The advantage of such cooperation is that it concentrates resources and brings together specialists, helping to speed the review process and avert the lengthy delays that occur in litigation.

Several cities, including Dallas and New York, have established similar units. Success, according to experts, depends on setting up rules that allow for the useful exchange of information and clear protocols on how cases will be reviewed and evidence evaluated. Also important are protections against prosecutors interpreting evidence with preconceptions that arise, however unintentionally, from their traditional roles. Mr. Machen told us that all the details haven’t been worked out and that, as a federal agency, his unit may operate under some constraints. But it is encouraging that his office consulted with nationally recognized experts, has conducted training to guard against the cognitive bias and plans to have the unit’s work reviewed by a committee that will include defense attorneys. The willingness of Mr. Machen’s office to be collaborative, not adversarial, was apparent in how it worked with the Mid-Atlantic Innocence Project to overturn the conviction of Kevin Martin in the rape and murder of a young woman in 1982.

Mr. Machen says he is setting up a unit that is intended to make a difference and not just offer the illusion of something being done. As he said in announcing his new unit, “As prosecutors, our goal is not to win convictions but to do justice.”