CHICAGO -- Illinois opened a marathon series of clemency hearings Tuesday for nearly every prisoner on death row in what could be the most sweeping review of capital punishment in U.S. history.

In all, more than 140 petitions for clemency will be heard before the end of next week. The hearings for all but a few of the state's 160 condemned inmates come after Gov. George Ryan said earlier this year that he intended to review every death penalty case before he leaves office in January.

"This is unprecedented," said Robert Dunne, a member of the Illinois Prisoner Review Board. "Normally we only hear petitions for clemency from death row inmates when their executions are imminent."

Ryan declared a moratorium on executions in 2000, calling the state's death penalty system "fraught with error" after 13 inmates were found to have been wrongfully convicted.

The board will make confidential recommendations to the governor. But Ryan has suggested that he may decide to grant a blanket clemency to all.