(Reuters) - The findings of a major study focusing on wrongful convictions released this week amount to an indictment of the American criminal justice system.

Misconduct by police, prosecutors and other officials contributed to more than half, 54%, of known wrongful convictions that led to exonerations in the past 30 years, according to the study released September 15 by the National Registry of Exonerations.

The organization examined 2,400 cases across the United States in which innocent people were convicted. Those cases are heavily weighted toward very serious crimes - cases that attract a great deal of attention and resources even post-conviction, and therefore yield a substantial record and plenty of information to re-examine for various purposes.

The findings, in other words, are the tip of an iceberg.

The sort of copious record-production we see in successful efforts to overturn a conviction "only happens in a small number of cases," Samuel Gross, one of the authors of the report and law professor emeritus at the University of Michigan, told me. "But what we know about these cases tells us a good deal about a much larger number, still a minority, but in which this kind of misconduct produces similar misjudgments."

Also notable in the study, the overwhelming majority of the officials who induced witnesses to give false evidence, coerced confessions from people during interrogations, and fabricated or concealed evidence, were never disciplined.

All together, the findings paint a picture nearly as damning as the videos of police officers doling out vicious physical abuse against citizens that have recently gained viral online audiences.

The Registry of Exonerations is jointly run by the University of Michigan Law School, Michigan State University College of Law and the University of California, Irvine, Newkirk Center for Science and Society. Northwestern University Pritzker School of Law, which helped co-found the organization, calls it the largest and most detailed compilation of U.S. exonerations data ever assembled.

The Registry's study found that police committed misconduct in 35% of the cases in which a convicted person was later exonerated, and prosecutors did so in 30% of those cases, according to the report.

Officials were more likely to commit misconduct in the most serious, often violent crimes, and misconduct was a driver of disproportionate rates of false convictions against Black people, the study found.

While Black defendants were only slightly more likely to be victims of official misconduct, generally, a full 47% of Black people wrongly convicted of drug crimes were convicted due to misconduct, compared with 22% for white defendants.

The Registry's study also found a gap in the rates of official misconduct when comparing Black and white defendants charged in death penalty cases, 87% versus 68%. Overall, despite making up just about 13% of the population, Black people account for 48% of all known convictions.

One case in the study provides a particularly egregious example. In 2006, Bobby Johnson, 16 years old at the time, pleaded guilty to murder after a police officer falsely told him they had evidence tying the boy to the crime, and that he'd get the death penalty and never see his family again if he didn't confess. The boy gave a rehearsed, taped confession. When evidence proved inconsistent, the police threatened him with losing a lenient (non-existent) plea deal unless he re-recorded the confession, which he did. Johnson was exonerated in 2015 due to new evidence, after the police officer was caught extracting other false confessions.

Perhaps most striking about the report, police officers were disciplined in only 17% of exonerations with known misconduct, and prosecutors just 4% of the time.

"The broadest and simplest conclusion is that misconduct by police officers, prosecutors and other law enforcement officials occurs on a regular basis and causes a steady stream of convictions of innocent people," Gross said.

Larry James, general counsel for the National Fraternal Order of Police and a former safety director for Columbus, Ohio, didn't address directly my questions about whether there's a systemic problem, but he offered this perspective:

"As long as human beings are involved in any aspect of exercising authority, there'll be situations where people run afoul" of the law or policies and guidelines, James said.

"I think most people in the law enforcement and prosecutors space would simply say those things are intolerable, you cannot have your judicial process tainted by any type of behavior that isn't objective and transparent," he told me. "The question is where and how do we impose checks and balances, and we have to advocate for that."

The report concerns 2,400 cases out of the "hundreds of thousands of convictions secured over the course of 30 years," Nelson Bunn, executive director of the National District Attorneys Association, noted. He said that increased oversight is a good way to help address the problem.

"Exonerations over the last three to five years have been the result of conviction integrity/review units created by prosecutors to take a proactive role in correcting injustices of the past," he said. "More and more offices are starting to create them, and we anticipate this trend will continue, which is a good best practice" to "ensure a fair and effective criminal justice system."

James also wants to see a stronger disciplinary regime. To quell misconduct, oversight bodies, and even other lawyers, should use ethics complaints and other disciplinary repercussions, including disbarment, as in the case of Mike Nifong, a former district attorney in North Carolina who was disbarred for concealing evidence in a news-making case against Duke University lacrosse students.

The absence of "negative incentives" for police and prosecutors is indeed a major hurdle, Gross said.

"We have a system in which some prosecutors have ambitions that go beyond their work in the office," Gross added. "Being successful in a major murder prosecution can lead to a political career, and that's a peculiarity of American politics."

The Registry's report shows that police officers and prosecutors are part of the problem in some of the worst, identifiable instances of system error. That, in turn, suggests a systemic approach is needed for policing the police.