Since 1989, more than 2,400 people have been exonerated, including at least 164 people who had been sentenced to death and 20 who were exonerated by DNA. We will never know how many innocent people have been executed in the U.S. We do know the evidence was very flimsy in many death-penalty cases in the 1980s and 1990s. We also know that public support for the death penalty continues to decline, for many reasons.