For years, Harris County was a big reason for the nation's climbing number of criminal exonerations, due to a backlog of drug cases in which testing showed defendants were actually innocent. As the county continues sifting through cases and finding fewer wrongful convictions, the national exoneration rate has dropped as well.

“We had this big surge of exonerations that was driven by [Harris County] efforts to rectify that,” said Barbara O’Brien, a Michigan State University law professor and editor of The National Registry of Exonerations, which on Wednesday released a report showing that Texas led the U.S. with 23 exonerees last year.

In 2014, the Conviction Integrity Unit of the Harris County District Attorney’s Office called for clearing a backlog of drug possession cases. Crime labs tested evidence from hundreds of cases and found that in many cases in which defendants had pleaded guilty, the substances seized by police weren't illegal drugs.

As a result, in 2016 Harris County exonerated 48 drug defendants; the number dropped to 10 last year, the report said. That helped push the national exoneration numbers down from 171 to 139 over the same period, the report found.

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Harris County District Attorney Kim Ogg told The Texas Tribune in 2017 that the county was working to fix a system that had been unfair to many defendants. 

“Historically, our drug laws have been enforced unequally, and I want to stop that,” Ogg said. “Obviously that’s going to require law enforcement leadership, training and policies that affect the way our laws are enforced, but as DA I can level the playing field by offering an equal opportunity to all offenders.”

The report also found that at least 96 convicted defendants in Chicago and Baltimore were declared innocent in group exonerations after evidence surfaced that police officers were systematically framing people for drug crimes.

Exoneration numbers have steadily climbed over time, thanks in part to more resources being devoted to conviction integrity units and innocence organizations that work to find and assist innocent defendants. In 2017, most exonerations were produced by such full-time “professional exonerators.”

But there’s still not enough resources, O’Brien said.

“If we had exponentially more CIUs and more innocence organizations that had the resources to investigate inquiries that they get, we would see who knows how many more exonerations we'd take,” O'Brien said. 

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