It looks like news of Harris County's bounty of wrongful convictions has gone international; the BBC did a piece on why they have lead the country in exonerations for the last two years. It's an interesting piece, and deals with the question of why seemingly small-time convictions, like drug possession, are such a big deal.
"Forty-two of those 2015 cases came from Harris County, the most from any single jurisdiction - the second runner-up is Brooklyn County, New York, with just 8. This is the second year in a row that Harris County - whose population is just shy of 4.5 million and encompasses the city of Houston - lead the report in sheer numbers. In 2014, it had 31, making it the exoneration capital of the US."
Check it out, it's worth a read.