Debra Milke was freed from death row in March. Photo: Jarod Opperman/dpa/Corbis

It’s not just Making a Murderer’s Steven Avery. A report released on Wednesday by a group called the National Registry of Exonerations revealed that 149 people — a record number — had convictions overturned in 2015, five of them from death row. That’s three a week, and the average stay in prison had been 14 years.

This makes 1,733 innocent people, and counting, freed in the U.S. since the National Registry started keeping track in 1989. The number of exonerations has doubled annually since 2011, in part because discoveries of false confessions and guilty pleas (which now account for more than half of all exonerations) are way up. One-third had been convicted of murder, and another third for drug possession. (Perhaps that’s not surprising, given that police field tests periodically identify vitamins, billiards chalk, and Jolly Ranchers as illegal drugs.) “DNA proves the wrong guy got fingered” cases, though attention-grabbing, account for less than 20 percent.

“This is not a problem that’s limited to a few counties,” the report says, adding, “By any reasonable accounting, there are tens of thousands of false convictions each year across the country, and many more that have accumulated over the decades.” But a full third of the exonerations (42 of them) were in one place — Harris County, Texas, which is essentially Houston — and therein lies a clue to what’s going on. Houston is one of 24 places in the U.S. that now has a Conviction Integrity Unit. CIUs are little units set up within the district attorney’s office to prevent or identify false convictions, and in the past five years they have quadrupled in number. More than a third of the bad convictions caught in 2015 were identified by these units, especially in Harris County but also in Brooklyn, which exonerated eight people last year.