Thousands of innocent Americans are spending years behind bars because of intentional misconduct by law enforcement and witnesses, according to the National Registry of Exonerations, a joint project of the University of Michigan Law School and the Center on Wrongful Convictions at Northwestern University School of Law.

Last year the Registry released its first report, which analyzes 873 exonerations between January 1989 and February 2012. In total, the 873 spent more than 10,000 years in prison for crimes they did not commit—an average of more than 11 years each.

According to the report, five of the most common reasons for wrongful convictions involved reckless or intentional misconduct, including perjury or false accusation (51%), mistaken witness identification (43%), official misconduct (42%), false or misleading forensic evidence (24%) and false confession (16%). (The numbers add up to more than 100% because many cases had two or more reasons behind them.)

The crime of murder spurred a higher rate of official misconduct (56%) than any other crime. Further, the shadow of misconduct lurks behind the leading cause of wrongful homicide convictions, which is perjury or false accusation (66%)–mostly deliberate misidentifications (44%)—and also explains the fact that homicide exonerations include 76% of all false confessions in the data.

In robbery and rape cases, mistaken eyewitness identifications are behind the overwhelming majority of bad convictions, including 80% of sexual assault cases and 81% of the robberies. In the rape cases, 53% of the bad I.D. exonerations involved white women accusing black men, a 10 to 1 racial disproportion probably caused by well-known difficulties of cross-racial eyewitness identification, a phenomenon itself arising from America’s troubled racial history.

Although most exonerations involved cases where the wrong person was convicted of a crime someone else committed, there were also cases where no crime was committed in the first place. Of child sex abuse exonerations, for example, 74% involved fabricated crimes that never occurred at all. But by far the largest concentrations of fabricated crime cases involve group exonerations following official misconduct. According to the report, at least 1,170 defendants were exonerated after authorities discovered 13 schemes in which police officers fabricated crimes, usually by planting contraband on innocent suspects.

Other highlights from the report include the following:

• 93% of those exonerated were men, 50% were black, 38% white, 11% Hispanic and 2% Native American or Asian.

• DNA evidence helped clear 37% of them.

• Since 2000, exonerations have averaged 52 a year, 40% of which include DNA evidence.

• The average time from conviction to a DNA exoneration is now about 18 years, up from less than 7 years in the early 1990s.

Since the report was issued, the registry has grown by 21.3% to more than 1,050 exonerations.

-Matt Bewig

To Learn More:

Exonerees: The numbers are small, but the toll is immense — and growing (by Tony Freemantle, Houston Chronicle)

Exonerations in the United States, 1989–2012 (by Samuel R. Gross and Michael Shaffer, National Registry of Exonerations) (pdf) 

DNA Clears Texas Man after 30 Years in Prison (by Noel Brinkerhoff, AllGov)

Innocent Man Released after 27 Years in Texas Prison (by David Wallechinsky, Noel Brinkerhoff, AllGov)