I still stand by my opinion that she will scrape together any little pieces of evidence to disprove Zimmerman's story in order to charge him with something. She will turn it over to someone else to prosecute and when it comes back with a not guilty verdict (due to lack of evidence) she will claim the other people messed up and it wasn't her fault. She is under HUGE pressure to press charges and arrest him, and I don't think her base will be pleased with some little manslaughter charges.
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Makes sense, trying to please everyone, without getting her hands dirty herself.