For centuries, scholars, judges and lawyers speculated about the error rate in the criminal justice system, many of them searching for absolute proof of the innocent person wrongfully convicted and imprisoned.  These efforts often proved futile, absent irrefutable evidence like in a nineteenth century case from Vermont in the United States.  In that case, two brothers were convicted of killing their brother-in-law after he went missing in 1812.  They spent seven years awaiting execution before their brother-in-law walked back into town very much alive.

But such cases were few and far between—and most observers remained skeptical about the existence of wrongful convictions.  The American jurist Learned Hand famously wrote in 1923 that the nation’s “procedure has always been haunted by the ghost of the innocent man convicted,” but went on to declare that “an unreal dream.”

This dream emerged as a nightmare reality in 1989 when the criminal justice system began to utilize nascent DNA technology.  Tests based on deoxyribonucleic acid (DNA) can pinpoint the genetic source of biological material with unprecedented accuracy, providing an opportunity to determine whether evidence from a crime scene (blood, saliva, semen and so on) belongs to a particular suspect.  In essence, DNA tests can serve to catch “the right guy” and free the “wrong guy.”

It is the second use of DNA – to free innocent prisoners – that is the subject of my recently published Cambridge University Press book: Wrongful Convictions and the DNA Revolution: Twenty-Five Years of Freeing the Innocent (2017).  This edited collection includes contributions from more than a dozen of the leading scholars on wrongful convictions in the United States.  It also features a foreword by Barry Scheck and Peter Neufeld, the co-founders of the Innocence Project in New York City, which is the world’s preeminent organization in the fight to free the innocent.  Specifically, the book focuses on two pivotal questions.  First, what have we learned from a quarter century of DNA exonerations? Second, given what we now know, what must be done in the prevent future miscarriages of justice?

Perhaps it’s naïve to think we can make the criminal justice system completely accurate.  As with all systems designed by humans, mistakes in processing criminal cases are inevitable; no matter what reforms we make, some innocent defendants will slip through the cracks and wind up behind bars.  But that shouldn’t stop us from trying: from implementing changes to reduce the risk of error if not to zero, then to something as close as possible to that magic number.


Read more about the scientific and legal advances of the past century in Daniel Medwed’s book, Wrongful Convictions and the DNA Revolution: Twenty-Five Years of Freeing the Innocent (2017).

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