Murder and manslaughter are State charges. I am not aware of any ability by the federal government to charge citizens with violation of any "civil right to live". The Police Officers in the Rodney King case were charged with civil rights violations because they were acting under color of law, or under their authority as Police. I will defer to an attorney who is familiar with this area of law, but I don't see it.
In any event, this would appear to be a violation of double jeapordy. There may yet be some legal action at the state level, and the parents of Martin will file a civil lawsuit.
I agree that manslaughter was the appropriate charge, but it was an included charge in the trial and apparently, at least in the eyes of the jury, it was not proved in trial. Zimmerman has been tried and aquitted. It is certainly not a perfect system, but it is the best we have.
It is my understanding, correct me if I am wrong, that Zimmerman testified that he lost sight of Martin, and then upon exitin his truck he was pysically attacked by Martin without warning. I don't know if there were witnesses to that beyond Mr. Zimmerman. I did hear a witness testifying that he saw what appeared to be Mr. Martin on top of Mr. Zimmerman striking him. This was apparently enough for the jury not to assign guilt to Mr. Zimmerman. So it appears to me that it was not the Zimmermans testimony of "fleeing" that caused the jury to come back with their verdict, but his testimony of a sudden physical attack without warning.
This is a judgement call in my opinion. A tough one for the jury. Mr. Martin is dead and could not present his own testament as to what happened. All the jury had was the evidence that was presented.
I don't see what laws should be changed. We live in an imperfect world. Of course no one's son is safe. No one is completely safe. Giving up liberties to chase "security" is a false hope. Your actions have consequences. Both Zimmerman and Martin's actions that night had consequences. A different choice at any stage leads to different results. This tragic case has been hijacked by others to be used for their own purposes. I see the language being repeated here... "wanna be cop", "wanna be thug", "twice his size", etc. and even worse. I don't believe there is a lot more to this other than a civil trial, which will award any monetary profit from this circus to the Martin family.