Wrongful convictions happen a lot

The journey also exposed me to the world of wrongful convictions, something that I, even as a former lawyer, had never spent much time thinking about. This is not a problem peculiar to Oklahoma, far from it. Wrongful convictions occur every month in every state in this country, and the reasons are all varied and all the same—bad police work, junk science, faulty eyewitness identifications, bad defense lawyers, lazy prosecutors, arrogant prosecutors.

John Grisham, The Innocent Man: Murder and Injustice in a Small Town (New York: Doubleday, 2006), p. 308.