Illinois has put a moratorium on the death penalty out of concern that innocent people are being sent to death row. But how common or how rare is such a tragic mistake?

• Experts say that the type of corruption that appears to have infested several convictions in Illinois hasn't been found in the 37 other states practicing capital punishment -- or in federal cases.

• A 1989 study by the Criminal Justice Legal Foundation, which reviewed 100 death penalty cases reaching the 11th Circuit Court of Appeals between 1986 and 1989, found only one in which a convicted murderer actually had a claim of innocence supported by some evidence.

• So in 99 percent of those cases there never was any real doubt about the guilt of the accused.

• Although every aspect of each death penalty case is scrutinized for several years following the trial and sentencing, on no occasion in the past 25 years has it been proved that an innocent person was put to death in the U.S.

Supreme Court Justice John Paul Stevens was never a death penalty advocate. But in a 1995 concurring opinion, he wrote: "The general rule... rests in part on the fact that habeas corpus petitions that advance a substantial claim of actual innocence are extremely rare."

In cases where it can be shown that serious mistakes were made in the arrest or trial, the conviction is overturned and the defendant is retried or set free.

Death penalty proponents point out that there are abundant safeguards in our legal system. And patently guilty murderers should not benefit from the mistakes made in rare instances in other cases.

Source: Michael Rushford (Criminal Justice Legal Foundation), "Faulty Convictions are Rare," USA Today, February 11, 2000.