The New Yorker is making all of its stories from 2007 to the present available for free for a few months. I highly, highly recommend this one:
http://www.newyorker.com/magazine/20.../trial-by-fire
Whatever one's feelings on the death penalty are, this article really makes it clear that often, state governments are not out for justice; they are out for convictions.
It's a really gripping read.