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A record number of convicts were exonerated last year, fueled by a backlog of lab tests that cleared drug suspects in Houston and a string of murder cases linked to a single New York City detective.

The National Registry of Exonerations recorded 125 in 2014 — up from 91 in each of the previous two years. The exonerees range from murder suspects convicted with tainted evidence to drug users who had their records wiped clean on a technicality.

The stage is set for an even higher number of exonerations next year because Harris County, Texas, is still working through a mountain of drug test results that could invalidate convictions.

"I've got about 400 reports," said Nicolas Hughes of the Harris County Public Defender's Office, who is handling the cases on behalf of the defendants. "My goal is to get them all done within this year."

He said dozens of people nabbed on drug charges in recent years took plea deals rather than wait in jail until lab tests came back. They may have gotten a lighter sentence for pleading guilty, but a drug conviction can make it hard to find housing or jobs.

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"These convictions can alter a person's destiny," Hughes said.

The problem was that the system for reviewing the test results and bringing them to the court's attention was broken, said Harris County Assistant District Attorney Inger Chandler.

Last April, a reporter from the Austin-American Statesman noticed the lab reports were coming back months or even years after a guilty plea and sentence and asked the DA's office about it.

In response, Chandler said, the system was streamlined. The lab now tests the substances as they come in, instead of putting guilty-plea specimens on the back burner, and prosecutors and the public defender's office work together to push writs through the courts.

She noted that in all the cases, the drugs field-tested positive for a controlled substance. In some, the person had bought bad dope; in others, the arrest report listed a different drug, a lower weight or a lesser strength. Her office is considering changing policy so no guilty pleas are taken before seized drugs are tested, she said.

Behind Texas, the state with the most exonerations was New York. Ten of those were in Brooklyn, and seven of those were tied to the work of retired NYPD Detective Louis Scarcella, according to the registry, which is a project of the University of Michigan Law School.

His cases were scrutinized after evidence he coached a witness led to the 2013 release of a man who served 23 years for a rabbi's murder. Those who won their freedom in 2014 include Jonathan Fleming, who spent almost 25 years in prison for a murder committed while he was at Disney World.

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