The way I see it, a man can change his name to a typically feminine name, and likewise a woman can do the opposite. They have the legal freedom to do so, but they're still a man/woman, whether they like it or not. So if I were to change my first name to Samantha, I'd just be a guy with a female name, so if he legally changed his name, use it. He should still be sent to the male prison where he actually belongs, though.