About 2 500 people are exonerated of great crimes after being falsely convicted over the past 30 years within the us .
According to a replacement study out yesterday, in about half their cases, police and prosecutors withheld evidence that might have exculpated them.
The study by the National Registry of Exoneration found that evidence that might have cleared the defendant was withheld in 61% of erroneous murder convictions.
And more broadly, 72% of exoneration cases during which the defendant was sentenced to death involved misconduct by police and prosecutors.
“Misconduct is usually more common the more extreme the violence,” the study says.
The report comes from a joint project of University of California-Irvine, the University of Michigan school of law and Michigan State University school of law .
It cites a broad range of police and prosecutor misconduct that contributes to unjust convictions: using questionable techniques to force false confessions, encouraging or coercing witnesses to supply evidence against a defendant; fabricating evidence; and prosecutors skirting the law.
African-Americans were slightly more likely than whites to be victims of misconduct resulting in false convictions.
But in some sorts of crime, blacks were much more often falsely convicted. In drug cases, blacks were 12 times more likely than whites to be falsely convicted.
Yet whites were also frequent victims, especially in so-called white-collar crimes involving corruption and fraud.