Exonerations in the United States, 1989 Through 2003: An aberration, or the tip of the iceberg?

One argument I frequently encounter is that wrongful convictions are rare, an aberration, and more is to be feared from guilty persons being acquitted than from innocent persons being convicted.

This study exposes the fallacy of that argument by comparing convictions/exonerations in robberies to convictions/exonerations in rapes (underlining added for emphasis).

Robbery and rape are both crimes of violence in which the perpetrator is often a stranger to the victim. As a result, robberies and rapes alike are susceptible to the well-known dangers of eyewitness misidentification.
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In 1987, a detailed study analyzed all known cases of eyewitness misidentification in the United States from 1900 through 1983, 136 in all. That study found that misidentifications in robberies outnumbered those in rapes by more than two to one; in fact, robberies accounted for more than half of all known cases of proven misidentifications.
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We have 121 exonerations in rape cases; in 88% of them (107/121) the defendant was the victim of eyewitness misidentification. But we have only six robbery exonerations, all of which
include eyewitness misidentifications. What changed? The answer is obvious: DNA. In 1987, the first DNA exoneration in the country was two years in the future. Since 1989, however, 87% of exonerated rape defendants were cleared by DNA evidence.

The implication is clear. If we had a technique for detecting false convictions in robberies that was comparable to DNA identification for rapes, robbery exonerations would greatly outnumber rape exonerations, and the total number of falsely convicted defendants who were exonerated would be several times what we report. And even among rape cases, DNA is only useful if testable samples of biological evidence were preserved and can be found, which is not always true.

In short, the clearest and most important lesson from the recent spike in rape exonerations is that the false convictions that come to light are the tip of an iceberg. Beneath the surface there are other undetected miscarriages of justice in rape cases without testable DNA, and a much larger group of undetected false convictions in robberies and other serious crimes of violence for which DNA identification is useless.

Another indication that wrongful convictions are far too commonplace comes from statistics provided by the March 2000 article, "Freeing the Innocent," by Barry Scheck, Peter Neufeld, and Jim Dwyer (underlining added for emphasis).

Today, DNA tests are used before trial. Of the first 18,000 results at the FBI and other crime laboratories, at least 5000 prime suspects were excluded before their cases were tried. Overall, more than 25 percent of the prime suspects could not be implicated because many, if not most, were innocent. For this unseen legion of innocent suspects, only the genetic tests halted their forced march from wrongly accused to wrongly convicted. How many other innocent people, charged with crimes that involve no biological evidence, were chained and led at gunpoint into prison? Thousands, these tests suggest, far more than the most jaded jurists or cynical scholars ever envisioned.