Those who research wrongful convictions have widely acknowleged the challenge of getting good statistics on the frequency of wrongful convictions. See "Wrongful Convictions and the Accuracy Of the Criminal Justice System" by H. Patrick Furman, and "Convicting the Innocent: An Empirically Justified Wrongful Conviction Rate" by D. Mcichael Risinger.
Risinger points out that the results of the Innocence Project provide a window of opportunity for empirical research on the wrongful conviction rate, at least as it applies to capital and other serious crimes where DNA evidence is available. Furman acknowleges the importance of such research, but raises an important consideration: can we expect the rate of wrongful conviction to be same for less serious crimes?
Peter Neufeld of the Innocence Project has had his faith shaken by the number of wrongful convictions uncovered. In an interview with PBS's Frontline, he says,
I always thought, my whole life I've been practicing law, especially as a criminal defense attorney that 98%, 99% of the people convicted by juries and judges must be guilty. And now I look at this new data which shows that with DNA testing they're exonerating 25% of the people accused in sexual assault cases and I'm completely freaked out by the number because it tells me that the number of people who are unjustly convicted in our system is extraordinarily high, is a number that we as a democracy can't live with, is a number that I want to do everything that I can to change.
Perception as well as empiricism, of course, is important in considering the level of accuracy in our justice system. What do the lawyers and judges think? How are their thoughts revealed in their language?
As we endured the investigation and trial of our son, we were shocked to hear professionals in the criminal justice system refer to a jury trial as a "roll of the dice." How, we wondered could trial by one's peers, something so valued in American culture be compared to a game of chance. When the verdict in our son's case arrived, we understood.
Moreover, the use of the phrase "roll of the dice" tells us that those in the best position to see how the system works have known its shortcomings for a long time.