As we learn more and more about wrongful convictions it is easier to know what to look for. The same goes for wrongful executions and the proof does not always require DNA. There is other powerful forensic evidence. The odds are that any state with the death penalty has committed a wrongful execution and the corollary is that a guilty killer went free. If you live in a state that has an archives, and you probably do, there are likely historical records that will help prove an execution correct or will prove a wrongful execution. These records may be in appeals or in commutation or pardon records. This research can be expensive. For example, it is $0.25 per page to have the archives staff copy and mail portions of a record in California. It would cost approximately $300 for them to copy and send the entire trial transcript. After learning what could be relevant through newspaper records I was able to request copies of specific testimony. But that was hit or miss because the actual testimony often didn’t cover what the newspapers implied it would or what I assumed it might. All my preliminary research was though the Internet, newspaper archives and these copy requests, but it wasn’t until visiting the California State Archives that I was able to put the research in concrete order with a firm foundation. The staff was professional and helpful and efficient. Google finds a great deal about the California States Archives and government records and the same is likely true for your state. If you discover what your state has to offer you could start researching wrongful executions.