In the introduction Bryan Stevenson lets the reader know that this will be a book about those whom society usually ignores. He believes society should be judged on that conduct. What a society does for those in need reflects its values.
Judge Key is trying to discourage Stephenson from taking on Walter McMillian's case. He knows that, if McMillian has good representation, it will be more difficult to railroad him. In fact, the judge's decision might even be overturned. This is something no judge wants to happen, since it makes them look bad. Stevenson will deal with this type of resistance throughout the book.