Many Prisoners on Death Row are Wrongfully Convicted

http://www.scientificamerican.com/article/many-prisoners-on-death-row-are-wrongfully-convicted/

Apr 28, 2014 |By Dina Fine Maron

Just how many individuals on death row are incorrectly convicted? The question has dogged attorneys and civil rights advocates for years, but a simple answer is almost impossible because few wrongful cases are ever overturned. A new analysis is adding a level of much-needed detail, and it concludes that more than twice as many inmates were wrongly convicted and sentenced to death than have been exonerated and freed.

Borrowing a statistical method often used to evaluate whether new medical therapies help patients survive, a team of researchers has concluded that about 4.1 percent of criminal defendants who are sentenced to death are falsely convicted. The approach allows researchers to “actually come up with a valid estimate of the rate of false convictions—knowing something that people say [in criminal justice] is not knowable,” says study author Samuel Gross, a law professor at the University of Michigan Law School and editor of the National Registry of Exonerations, a U.S.-focused exoneration database. What makes the analysis possible is that data on the potential need for exoneration from death penalty cases come to light more often than it does for other types of criminal proceedings. All death sentences in the U.S. are based on crimes that include homicide.

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The issue affects a significant number of people. Since 1973 144 death-sentenced defendants have been exonerated in the U.S. But Gross says that the analysis indicates that at least 340 people would have been put to death unjustly in that same time period.

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The researchers also note that a 4.1 percent rate of false conviction is conservative

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