Story highlights Hundreds of convicted U.S. prisoners have been freed after DNA testing cleared their names

Some of these prisoners faced the death penalty before they were exonerated

Advances in testing of genetic material have opened door to further examination of cases

two decades, During the pasttwo decades, the Innocence Project and other advocates have been utilizing rapid advances in the scientific testing of genetic materials.

DNA testing of evidence in criminal cases has resulted in freedom for hundreds of prisoners across the United States who were wrongfully convicted.

Many of these prisoners spent years behind bars -- some even faced the death penalty -- for crimes they didn't commit.

Here are a few of the numbers behind these exonerations:

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--Number of prisoners sentenced to death before DNA proved their innocence: 18

--Number of prisoners charged with capital crimes but not sentenced to death: 16

--Average length of sentence served by DNA exonerees: 13.6 years



--Approximate total years served by all DNA exonerees: 4,156

--Average age of exonerees at the time of their wrongful convictions: 27

Graph: Freed by DNA testing

--Percentage of prisoners exonerated by DNA testing who are people of color: 70%

--Percentage of DNA exoneration cases where the actual perpetrator has been identified by DNA testing: Almost 50%

--Number of DNA exonerees who pleaded guilty to crimes they didn't commit: 29

--Number of DNA exonerations that involved the Innocence Project: 171

--Year of the first Innocence Project DNA exoneration: 1989

Note: Other exonerations were helped by Innocence Network organizations, private attorneys and by pro se defendants, according to the Innocence Project.