Inmates walk through the exercise yard at California State Prison Sacramento, near Folsom, Calif. (AP/Rich Pedroncelli)

A California research project tried to do something no one’s ever done: determine the total cost of wrongful convictions. That cost being not just the settlements paid to innocent defendants, but the unnecessary costs of prosecuting and incarcerating them, plus the total legal bills of their criminal trials and appeals.

Beginning the project in 2012 and working backwards to 1989, the study found 692 people who were convicted of felonies in California but whose cases were later dismissed or acquitted on retrial. Those people spent a total of 2,346 years in custody and cost California taxpayers an estimated $282 million when adjusted for inflation, according to the Chief Justice Earl Warren Institute on Law and Social Policy at the University of California, Berkeley School of Law, which released the study last week.

Now for some scale: Those 692 failed convictions over 24 years were part of a California system that convicts more than 200,000 people every year. Some may argue, the report notes, that 692 mistakes over more than two decades “reflects an acceptable rate of error. We reject the proposition that an acceptable rate of error can apply to proceedings that impact people’s lives in the way that criminal prosecution can…Just as with airline safety and medical mistakes, the acceptable rate of error is zero and that should be the goal.”

The researchers also note that they almost certainly did not find every case where a conviction was reversed, and that some county courthouses in California were more difficult than others to extract data from over the three-year project. Both state and federal courts were used, and the study did not include cases where defendants were tried and acquitted, or arrested but later had charges dismissed.

Some other interesting findings: The study documented that taxpayers shelled out $68 million in civil settlements. Of the 692 exonerated defendants, 85 emerged from the Rampart scandal of Los Angeles police corruption in the late 1990s. Violent crimes were disproportionately represented, involving 30 percent of the exonerated defendants, though only about 18 percent of California felony convictions are for violent crime. Homicide cases were the most expensive mistakes, with 92 cases costing 52 percent of the total money spent on wrongful prosecutions. And though only two percent of California criminal cases result in a trial, 74 percent of the exonerees in the study went to trial.

Rebecca Silbert, the executive director of the Warren Institute and one of the study’s authors, said she was “very surprised by the sheer numbers of days and years spent in jail” by those wrongly convicted. The researchers then used a formula to determine the daily cost of housing the exonerees in jails or prisons, and found that cost to be $80 million, plus another $5 million paid as compensation for wrongful imprisonment, in addition to the $68 million in lawsuit settlements. The costs of trials and appeals, also calculated by using costs of court personnel, prosecutors and public defenders, was estimated at $68 million.

Public interest in these issues has mushroomed since the study was launched in 2012. “I didn’t think anyone was going to be interested,” Silbert said. “For so many years, criminal justice and the ways it doesn’t function well was thought of as someone else’s problem.”

The study, titled “Criminal Injustice: A Cost Analysis of Wrongful Convictions, Errors and Failed Prosecutions in California’s Criminal Justice System,” did not attempt to assess the costs to the incarcerated defendants from the lost years of their lives or the impact on their families and their future earnings potential. But the sentences received by those in the study were disproportionately severe, with 19 percent sentenced to life in prison and another 11 percent sentenced to at least 10 years. The study also did not try to assess the race of the defendants due to unreliable court data.

On average, the defendants in the study spent 4 1/2 years in prison, but 58 of them spent more than 10 years wrongly incarcerated, and one — Kash Delano Register — spent 34 years in prison. In January, the city of Los Angeles agreed to pay Register $16.7 million, and they paid $7.6 million to another man who spent 26 years behind bars, both because of flawed police investigations and prosecutions.

The researchers broke down the causes of the wrongful convictions into eight categories: judicial mistake, failure of prosecutorial discretion, ineffective assistance of defense counsel, eyewitness misidentification, inadequate police practices, improper search and seizure, prosecutorial misconduct, and unreliable or untruthful testimony by a police officer or informant. Prosecutorial misconduct accounted for 11 percent of the bad convictions but 24 percent of the total cost. Judicial mistakes accounted for the most error, 22 percent, and 14 percent of the total cost.

Numerous individual case examples are cited, and the researchers reviewed each case file by hand. And because the study required individual case review, the actual dollar amount of settlements paid is likely much higher. The Rampart scandal, in which officers framed hundreds of innocent citizens, resulted in 228 civil settlements paid by Los Angeles, with verdicts and settlements totaling more than $78 million. But trying to track down all of the cases proved problematic due to deficient record-keeping by the L.A. courts, and the study was only able to find 85 cases totaling $54 million. Estimates made by other media have calculated the cost of Rampart at between $125 million and $1 billion.

The authors make a series of recommendations to reduce or eliminate wrongful convictions, such as allowing civil litigation against prosecutors’ officers that engage in misconduct; greatly improving techniques for the use of eyewitnesses; increased resources for prosecutors and defenders to reduce judicial mistakes; and improved police training to reduce illegal searches and seizures.

The full report can be found here.