False convictions are notoriously difficult to study because they can neither be observed when they occur nor identified after the fact by any plausible research strategy. Our best shot is to collect data on those that come to light in legal proceedings that result in the exoneration of the convicted defendants. In May 2012, the National Registry of Exonerations released its first report, covering 873 exonerations from January 1989 through February 2012. By October 15, 2016, we had added 1,027 cases: 599 exonerations since March 1, 2012, and 428 that had already happened when we issued our initial report but were not known to us. In this paper I discuss what can and cannot be learned from the exonerations that we have collected. The cases we find and list are not a complete set of all exonerations that occur—not nearly—but it’s clear from the patterns we see in known exonerations that false convictions outnumber exonerations by orders of magnitude. We cannot estimate the rate of false convictions or their distribution across crime categories. We can confidently say, however, that they are not rare events—and other research has estimated the rate of false convictions among death sentences at 4.1%, which provides an anchor for estimates of the rate for other violent crimes. We know that several types of false or misleading evidence contribute to many erroneous convictions (eyewitness misidentifications, false confessions, bad forensic science, perjury and other lies), as does misbehavior by those who process criminal cases: misconduct by police and prosecutors; incompetence and laziness by defense attorneys. Beyond that, we cannot say how false convictions are produced. It’s clear, however, from the relative prevalence of these factors that the process differs radically from one type of crime to another. Data from one local jurisdiction (Harris County, Texas) strongly suggest that across the country thousands if not tens of thousands of innocent defendants a year plead guilty to misdemeanors and low-level felonies in order to avoid prolonged pretrial detention. And our data clearly show that innocent African Americans are much more likely to be wrongfully convicted of crimes than innocent whites, in part because of higher criminal participation in the African American community and in part because of discrimination.
Gross, Samuel R. "What We Think, What We Know and What We Think We Know about False Convictions." Ohio J. of Crim. L 14, no. 2 (2017): 753-86.