How Many Innocents?
It has become common to see reports of people being released from prison after establishing their innocence. The majority of those cases involve DNA evidence, which is not suprising. Almost no one can argue with the results of a scientic test that can establish someone did not commit an offense. Unfortunately, DNA testing can only be done in a small number of cases, and there are no such tests that can be used in other types of cases.
Since it is now accepted that innocent persons are convicted, many people wonder how many innocent persons there are in prisons across the country. A few people have tried to come up with formulas to determine how often innocent persons are convicted. Some people have argued the rate is somewhere between .27% and .65%. However, the process for coming up with those numbers often does not account for the limited number cases in which scientific evidence is available. To come up with an accurate number, you would have to compare the number of exonerations with the number of sexual assault and murder convictions, since those are the type of cases in which physical evidence is often available. Of course, some allowance has to be made for the number of cases that are not tested, since only a handful of cases are ever subject to post-conviction review.
Recently, the Virginia Department of Forensic Science found a number of closed rape cases with untested DNA evidence. So far, out of 29 cases tested, 2 wrongful convictions have been uncovered. If that ratio remains consistent, the error rate would be 7%. A review of death cases by law professor at Seton Hall University produced an error rate of 2.3%. While those percentages might seem low, the real life affects are enormous; With a 2% error rate, there are 20 innocent persons for every 1,000 convictions.
