What are some famous criminal investigations in which procedure was not followed?

I have to do a research paper for my CSI323 course and I need to do an ysis of a criminal court case. More specifically it needs to be a criminal investigation wherein proper procedures and/or techniques were possibly not followed by the investigating officers. I would like to yze a case that received some media attention, however I want to avoid cases like OJ Simpson or Jean Bennett Ramsey. Any suggestions?