The Falsely Convicted Spend Years In Jail Before Exonerations, And They Are the Lucky Ones.

The overall average is 11.9 years from conviction to exoneration, 13.0 years from arrest. The range varies greatly. Exoneration generally takes long when the crime is more serious.

Black defendants are heavily overrepresented among exonerees: they are heavily overrepresented among those arrested and imprisoned for violent crimes and drug crimes. But the disproportions we see are greater than what one would expect. In 2000, for example, 46% of state and federal prisoners were black; in 2008, that  proportion was 38%.42Using either bench mark, black exonerees, at 50%, are somewhat overrepresented among all exonerees -- but this disparity is unevenly distributed. In 2008, 43% of homicide prisoners were black,43 only slightly fewer than the 49% of homicide exonerees who were black. For robbery, the difference is greater: 52% of prisoners and 64% of exonerees were black; for drug crimes, 45% of prisoners and 60% of exonerees were black (but the number of cases is small). Finally, for sexual assault, the difference is huge: 25% of prisoners, but 63% of exonerees were black.

The 873 exonerations in the Registry come from 43 states, the District of Columbia, the  Commonwealth of Puerto Rico, 19 federal districts, and the military. They are very unevenly distributed by state, and especially when broke down by county. This suggests we are missing many cases -- both innocent defendants from jurisdictions where exonerations are vanishingly rare, and exonerated defendants whose cases have received little or no public attention.  Two-thirds of all exonerations occur in just 10 states. In the most recent report, Excluding Federal cases, the top 10 states account for 64% of all exonerations. They are: 

There is a well-known list of factors that are associated with exonerations: eyewitness  misidentification, false confession, perjury, false or misleading forensic evidence, official  misconduct.  More than one factor may be present in a false conviction.  For all exonerations, the most common causal factors are perjury or false accusation (51%), mistaken eyewitness identification (43%), and official misconduct (42%).  For 104 exonerations, our information includes clear evidence of severely inadequate legal defense, but we believe that many more of the exonerated defendants -- perhaps a clear majority -- would not have been convicted in the first instance if their lawyers had done good work.

CONCLUSIONS (In full from this report)

The most important thing we know about false convictions is that they happen and on a regular basis. We don't know how often they occur or what types of cases are most common. Most false convictions never see the light of day. We know only about the rare ones that are discovered and corrected (at least in part) by exoneration -- and we miss many cases in which innocent defendants are exonerated, probably most. We do know that the more we look, the more exonerations we find, and the more varied they are.

The most important goal of the criminal justice system is accuracy: to identify and condemn the guilty, and to clear the innocent. The most effective way to do so is by careful, honest and open minded work before conviction, in the investigation and prosecution of criminal charges.

The next most important task is to remain open minded after conviction about the possibility of error. The overwhelming majority of convicted defendants are guilty. Most never dispute their guilt and few ever present substantial post-conviction evidence of innocence. When that does happen, however, it should be taken seriously. We know of many exonerated defendants who were imprisoned for years, even decades after they presented strong evidence of their innocence.  We cannot prevent all false convictions, but we must not compound these tragedies by stubbornness or arrogance or, worst of all, indifference.

The National Registry of Exonerations is the largest database of its kind ever assembled. We have already learned a great deal from it. In particular, it is now clear that false convictions are not one sort of problem but several, and that the solutions that might prevent them vary drastically from one context to another: For homicides, the biggest problem is perjury and false accusation, most often by supposed eyewitnesses, with official misconduct a close second. False convictions in adult rape cases, on the other hand, are primarily based on eyewitness mistakes -- more often than not, mistakes by white victims falsely identifying black defendants. Most false convictions in child sex abuse cases, by contrast, are for fabricated crimes that never occurred, and so forth.   We will learn more as the Registry matures and we gather data about a larger number of  exonerations across a wider range of settings. The more we learn about false convictions the better able we will be to prevent them, or failing that, to identify and correct them after the fact.