Convicting the Innocent studies the cases of 150 people who did serious prison time and have since been proven innocent beyond a reasonable doubt by DNA evidence. It shows the problems with confessions, eyewitness testimony, and perhaps worst of all, jailhouse snitches.
For a long time, I was neutral on the death penalty. I don't have strong feelings about it, but most people do, in ways that cannot be settled by further factual evidence. What I do have strong feelings about is making sure we've got the actual perp, especially if we're going to kill the person we convict, and this book, and the specific case of Troy Davis, have convinced me that as long as there's a death penalty, we're going to kill innocent people, or at least people we aren't sure enough about.