South Hadley, Mass.

LAST week, Judge Nancy Gertner of the Federal District Court in Boston awarded more than $100 million to four men whom the F.B.I. framed for the 1965 murder of Edward Deegan, a local gangster. It was compensation for the 30 years the men spent behind bars while agents withheld evidence that would have cleared them and put the real killer — a valuable F.B.I. informant, by the name of Vincent Flemmi — in prison.

Most coverage of the story described it as a bizarre exception in the history of law enforcement. Unfortunately, this kind of behavior by those whose sworn duty it is to uphold the law is all too common. In state courts, where most death sentences are handed down, it occurs regularly.

My recently completed study of the 124 exonerations of death row inmates in America from 1973 to 2007 indicated that 80, or about two-thirds, of their so-called wrongful convictions resulted not from good-faith mistakes or errors but from intentional, willful, malicious prosecutions by criminal justice personnel. (There were four cases in which a determination could not be made one way or another.)

Yet too often this behavior is not singled out and identified for what it is. When a prosecutor puts a witness on the stand whom he knows to be lying, or fails to turn over evidence favorable to the defense, or when a police officer manufactures or destroys evidence to further the likelihood of a conviction, then it is deceptive to term these conscious violations of the law — all of which I found in my research — as merely mistakes or errors.