/ Updated 
By Tim Stelloh

A pair of reports released Tuesday examining wrongful convictions in the United States found that there were a record number of exonerations in 2016 — the third such record-setting year in a row — and that innocent black people face a raft of racial disparities that make them more likely to wind up behind bars, and to remain there longer than whites.

Researchers at the National Registry of Exonerations, which is run by the University of California, the University of Michigan and Michigan State, published the data.

Mildred Pinkins and her son Darryl Pinkins embrace outside the Lake County Jail in Crown Pointe, Ind., after he was released on April 25, 2016 after serving more than two decades in prison for a gang rape in which he was recently cleared.Tony V. Martin / The Times via AP

Samuel Gross, a law professor at the University of Michigan and an author of the race study, attributed the growing number of exonerations to increased awareness and resources, and he said they were part of persistent pattern: the number of exonerations climbed to 166 last year, up from 149 the year before and more than double the number of cases in 2011.

The registry has collected data on nearly 2,000 cases since 1989.

Researchers found that racial disparities disproportionately impacted black people across the three crimes they examined — murder, sexual assault and drug charges. Innocent blacks, for instance, were seven times more likely to be convicted of murder than innocent whites and three-and-a-half times more likely to be convicted of sexual assault.

Once convicted of the latter, the researchers found, wrongly convicted black people spent four-and-a-half years longer in prison than whites.

Related: He Survived a False Conviction but Freedom Failed Him

Cross-racial mis-identification was frequently what put them there to begin with — particularly “a core problem” among white female victims wrongly accusing black men, Gross said — but those black men who refused to plead guilty also received longer sentences than their white counterparts.

Then, Gross added, “there was more resistance to releasing them once other evidence began to emerge.”

Researchers attributed 70 of the 166 exonerations across 25 states last year to specialized units within prosecutors' offices. That number is a record, thanks in part to the quintupling of so-called Conviction Integrity Units since 2011.

Related: The Reasons Behind Wrongful Convictions

The 70 wrongful convictions involving official misconduct also set a record last year. The most common form, researchers found, involved police and prosecutors concealing evidence.

There were a record number of overturned drug cases in 2016 as well — 61, up from 43 in 2014 — with the vast majority of them occurring in Harris County. A program there was started three years ago to clear defendants who plead guilty to possessing illegal substances — even though a crime lab analysis would later contradict the original drug charge.

Gross said that faulty drug testing kits were behind those charges. Recalling a case in which kitty litter was misidentified as cocaine, he said: “Those tests are very often totally inaccurate. But they’re good enough to arrest people.”