Martin went three quarters of the way around the block to turn an encounter into an unnecessary confrontation. He smashed a man's head repeatedly against the pavement without justification, for which he could have been charged with assault with a deadly weapon, had he lived. These facts were presented to the jury.
George Zimmerman had a history of tutoring youths, white and black alike. He ran a public campaign to prosecute a boy--the son of a white cop--who had attacked a black neighbor youth, and who was apparently being protected by the blue shield. (The campaign was successful.) He left his truck to carry out the directions of the police dispatcher, and he was returning to his truck, also under instructions of the dispatcher, when he was attacked.
Bill Whittle presents the case here:
http://m.youtube.com/watch%3Fv%3DEbu6Yv … Y8_gCxLnlg . You can say that the liver damage does not prove drug abuse, and you'd be right. But it's consistant with it, and Martin's own web posts strongly indicate that he was a user.
Reports of Martin's character indicate that it changed greatly in the previous few years. The changes are consistant with (again, not proving) the drug cocktail which he himself said he (mis)used. The personality changes that are reported to follow from abuse of that drug are also consistant with his behavior on the night he attempted to kill a witness, and lost his life in the attempt.
Blame his environment if you must; there's no doubt he was failed by a school system more concerned with hiding its failures than protecting its charges. But he attempted to kill a witness to his presence, and lost his life in the attempt.