Q. How many innocent people are there in prison?
A. We will never know for sure, but the few studies that have been done estimate that between 2.3% and 5% of all prisoners in the U.S. are innocent (for context, if just 1% of all prisoners are innocent, that would mean that more than 20,000 innocent people are in prison).
More broadly, we know that innocent people are often identified as suspects by law enforcement and that DNA testing often clears them before they go to trial, but that DNA testing is impossible in the vast majority of criminal cases. In approximately 25% of cases where DNA testing was done by the FBI during the course of investigations, suspects were excluded by the testing. That doesn’t mean we believe 25% of convictions are in error, but when coupled with the fact that DNA testing is only possible in 5-10% of all criminal cases, it shows that science cannot always clear innocent suspects, which can result in wrongful convictions.