WASHINGTON -- The American system of capital punishment has taken the lives of 16 men despite "compelling evidence of their innocence," according to a report by death penalty foes scheduled to be released Thursday.

"Courts overwhelmingly favored procedure over justice and efficiency over fairness," the report by Equal Justice USA contends. "In doing so, state and federal governments sanctioned the state killing of men who were probably innocent."

 The report is the product of a grass-roots investigation project, in which anti-death penalty activists in several states conducted research into cases where there were doubts about an executed inmate's guilt. The individual state researchers then forwarded their findings to Equal Justice, a liberal public-interest group that sponsored the survey.

 Supporters of the death penalty reacted with skepticism to news of the report.

 "Every prosecutor's worst nightmare is that an innocent person could be executed," said Joshua K. Marquis, an Oregon district attorney who serves as a spokesman for the National District Attorneys' Association.

 "It takes 10 or 12 or 14 years for these cases to get through the courts, and rightfully so," said Marquis. "We could always do a better job, but the idea that people are regularly being clapped into death row after being represented at their trials by drunken lawyers six months out of law school is a reality that doesn't exist. It may have at one time, but it does not exist now."

 The Equal Justice report introduces no new evidence in the 16 cases -- no new forensic or DNA tests or witness recantations -- but instead tracks each case through the state and federal court systems from the day of the crime to the day of the execution, raising questions at various stages about the accuracy and fairness of the process.

 The report cites the case of Larry Griffin, for example, who was executed by the state of Missouri in 1995. A major part of the prosecution's case was the testimony of one eyewitness -- a Boston hoodlum with a lengthy criminal record named Bobby Fitzgerald.

 Fitzgerald was living a new life in the federal witness protection program, after testifying against his former criminal associates in Boston, when he happened to observe a drive-by shooting in St. Louis. He identified Griffin from a police photo lineup.

 The jury at Griffin's trial was told almost nothing about Fitzgerald's criminal record and history as a government witness, or that he was being held by St. Louis authorities on fresh charges of credit card fraud. After Fitzgerald testified, the prosecution agreed to settle the credit card case with no further jail time. Fitzgerald later recanted much of his testimony.

 Though Griffin had a motive -- the victim was a drug dealer who was said to have shot Griffin's brother -- there was no physical evidence linking him to the crime.

 Griffin's lawyer was just a few years out of law school, and had never tried a murder case. Another federally protected witness from a federal racketeering trial later identified three other men as the killers.

 "This report represents only a small number of the actual cases in which people have been executed for crimes they probably did not commit," the Equal Justice organization said.

 The Equal Justice report, which was compiled by Maine writer and activist Claudia Whitman, cites incompetent and poorly paid defense attorneys; prosecutorial and police misconduct; racial bias and judicial timidity as the prime failures of the death penalty system.

The executed men identified as innocent are Brian K. Baldwin, Cornelius Singleton and Freddie Lee Wright of Alabama; Thomas M. Thompson of California; James Adams, Willie Darden and Jesse Tafero of Florida; Girvies Davis of Illinois; Griffin and Roy Roberts of Missouri; Odell Barnes, Robert N. Drew, Gary Graham, Richard W. Jones and Frank B. McFarland of Texas; and Roger K. Coleman of Virginia.