@JTT,
Part of the problem is faulty eye-witness identifications, particularly in black-on-white crimes. I believe these arise in cases of white witnesses who have never been around black people enough to have any sort of a feel for identifying them, and in some cases apparently couldn't tell the difference between two blacks if one were male and the other female or one alive and the other dead. I don't have any sort of a theory as to what the cure for that one might be.