I will do my best to find the articles I mentioned from the New Yorker to provide them for you.  One of them is about a particular prisoner who studied the law while incarcerated, and began - in prison - a service to file an appeal for a new trial based on evidence withheld by prosecutors, or discovered after the crime (such as DNA or the recanting of statements by witnesses) that wasn't allowed to be entered into the court deliberations.  That inmate had some real success in doing this work, and once he gained his own freedom using the same studious methods, he joined with an existing legal project doing the same type of work for individuals wrongly convicted.  There are so many procedural errors made, so many cases of prosecutors refusing to reconsider the case in view of new evidence, and so very many cases of poor evidence gathering by police, it makes one cringe at the failures of our legal system.