I know there has been one case this year where the trans panic was succesful, but I'm afraid a crusory run around google can't find it.
My apologies, but this sort of thing strikes kinda close and it becomes a bit personal. keep to the Fen Causeway
Even if the panic could be understood (certainly not justified, but let's for a moment consider understandability), how could a judge justify the link between panic and killing. It's identity anxiety maybe, but the person is under no threat whatsoever.
It reminds me (don't take it badly) of Terry Pratchett when Rincewind and Bethan are struck that, when Cohen the Barbarian is afraid of someone or something, he tries to fight. But he's a novel character and, precisely, a barbarian. "Few can believe that suffering, especially by others, is in vain. - Galbraith"