A record number of people were exonerated in the United States last year, after serving time in prisons for crimes they did not commit. According to a report released Wednesday by the National Registry of Exonerations — a project of the University of Michigan Law School — 149 people were exonerated in 2015, topping the previous record of 139 in 2014.

“Not long ago, any exoneration we heard about was major news. Now it’s a familiar story,” the report stated. “We average nearly three exonerations a week, and most get little attention.”

According to the report, which comes at a time when calls to reform the country’s criminal justice system are growing louder, of the record 58 people exonerated in homicide cases in 2015, over two-thirds were minorities, including half who were African-Americans.

In all, the 149 people exonerated in 2015 had spent an average of about 14-and-a-half years in prison. Five of those wrongfully convicted had been sentenced to death, while 14 were sentenced to life in prison without the possibility of parole.

“The most striking thing about these exonerations, however, is the nature of the underlying convictions. The list of exonerations in 2015 includes record numbers of homicide cases with false confessions and official misconduct, with convictions based on guilty pleas, and cases in which no crime in fact occurred,” the report said.

A record 27 exonerations in 2015 were found to be for convictions based on false confessions. And, most of those who had falsely confessed to a crime, including homicide, were either children, mentally handicapped, or both.

“Exonerations in cases in which defendants pled guilty used to be rare, but they have become more common in the last seven years and much more so in the past two years. In 2015, 44 percent of all exonerations were in guilty plea cases, more than any previous year,” the report stated.

For instance, in the case of drug-related crimes — for which 51 people were exonerated in 2015 — many people likely pleaded guilty despite their innocence and agreed to plea bargains in order to avoid long prison terms.

The report attributed the surge in the number of exonerations to an increase in the number of prosecutors revisiting old convictions. For example, over 28 percent of all exonerations last year came from Harris County, Texas, because it has rigorously reviewed past convictions and found that aggressive tactics such as threatening defendants with long prison terms to secure guilty pleas, led many to plead guilty to crimes they didn’t commit.

“The Harris County drug guilty-plea exonerations are a window into the world of plea bargaining in misdemeanors and comparatively light felonies across the country,” the report stated.