Just adding to the "Gin's ending was a half-assed attempt at redemption" point.
Remember that time Ichigo's dad showed up and did squat along with Urahaha and Yoruichy? Gin was supposed to be fighting Ichigo and was instead giving him pointers on how to fight and talks about his faltering resolve and what not. I think that's what his last lines of "your eyes look strong now blah blah" to Ichigo are supposed to refer to, pulling off a Snape; a shoddy one at that. A poor man's Snape, if you will.
So if he was supposed to be a good guy all along, who is to take the fall for the guy he killed just to get Aizen's recognition? He wasn't just some low level fodder either. The 3rd seat if memory serves right. That guy must have had a family, friends, dreams and ambitions of his own. Is it any different than the charges being levelled against Sasuke?