Exonerated: wrongful convictions overturned and the lessons we can learn

Wrongful convictions are as old as justice itself, and any system of criminal justice is a human endeavor, which will inevitably make mistakes. However, it wasn't until the advent of DNA testing that these mistakes were exposed beyond a shadow of a doubt. DNA has changed the criminal justice system forever: thousands of people have been convicted based on DNA evidence, and more than 220 have been exonerated. Other forms of evidence have also overturned thousands of convictions, but the standard is proof in non-DNA cases is much, much higher.

DNA exonerations have sparked a period of rapid reform in the American criminal justice system; by exonerating the innocent they have illuminated the unreliability of certain types of formerly convincing evidence - like eyewitness identification and false confessions. But DNA testing isn't a panacea, and although its lessons could prevent wrongful convictions down the road, it offers little help to innocent inmates without DNA evidence to test. Since only about 10 percent of felony convictions involve biological evidence, many experts believe that there are thousands of wrongfully convicted people in prison today without the benefit of DNA evidence to prove their innocence. For the other 90 percent, proving innocence after a jury or judge has found guilt is all the more difficult. Our system is built to establish facts at trial and then trust those facts through the appeal process, so even defendants with strong evidence of innocence are sometimes denied a chance to present that evidence on purely procedural grounds.

Below are four examples of cases in which American prisoners were able to overturn wrongful convictions by presenting new evidence of their innocence - and one case in which evidence strongly suggested the innocence of a Texas man after he was executed.

(Full disclosure, I work at the Innocence Project, which was involved in the cases below, either as primary appellate counsel or in a consulting role.)

Kirk Bloodsworth was the first person exonerated by DNA evidence after serving time on death row. He was convicted of a murder he didn't commit in Maryland in 1985 and sentenced to death. After his conviction, Bloodsworth's attorneys found that police had withheld information about a possible alternate suspect, and based on this and other new evidence, he was granted a new trial. Unfortunately, he was convicted again, this time sentenced to life in prison. It wasn't until 1993, when he had served eight years in prison, that DNA testing proved Bloodsworth's innocence and led to his release. Today, he works as a program officer at the Justice Project and is the subject of Tim Junkin's "Bloodsworth: The True Story of the First Death Row Inmate Exonerated by DNA."

Jerry Miller was exonerated in 2007 in Illinois after serving 25 years in Illinois prison for a rape he didn't commit, making him the 200^th person cleared by DNA testing in the U.S.. He was misidentified by witnesses in a police lineup, a factor shared by 75% of wrongful convictions overturned by DNA testing. Watch an interview with Miller on YouTube here.

Dennis Fritz and Ron Williamson were convicted of a murder they didn't commit in Ada, Oklahoma in 1988. Some of the most persuasive evidence against the men at trial came from jailhouse informants, who testified that Fritz and Williamson had confessed to them while they shared cells. Informants, especially those receiving a sentence reduction or other incentive for their testimony, are notoriously unreliable witnesses. The men served 11 years in prison - Williamson was on death row - before DNA testing proved their innocence. In 2006, John Grisham published a book about the cases, "The Innocent Man."

Marty Tankleff was freed in 2007 after serving 17 years in prison for allegedly killing his parents at their Long Island, New York, home.  After hours of questioning, Tankleff wondered if could have blacked out and committed the crime. Detectives read him his rights at this time, and drew up a "confession," which Tankleff immediately recanted and never signed. Based on his alleged false admission (false confessions and admissions account for 25% of wrongful convictions overturned by DNA testing, and young people are particularly susceptible), Tankleff was convicted and sentenced to 50 years to life. While there was no DNA evidence in Tankleff's case, a sweeping investigation by his attorneys found convincing evidence of his innocence, and a New York judge overturned his conviction in late 2007, leading to his release.

Cameron Todd Willingham was executed in Texas in 2004 for allegedly setting the fire that killed his three children.  He was convicted based on arson science that has since been debunked. A panel of arson experts recently found that the science used to convict Willingham was faulty and that Texas may have executed an innocent man. An investigation into the case - and into hundreds of questionable arson convictions around the country - is currently ongoing.