As far as people were concerned, Amelia Wonderley was dead. But the body that was found wasn't hers, though. It had to look similar so that people could believe it was her, so she killed a woman to get a corpse to pass as the "fake" Amelia. Normally, I wouldn't try finding out who she killed, but the fact that she uses Trucy's appearance is what made me click. According to her brother, she didn't use surgery or anything advanced, so if she were to pass as someone else, it'd need to be someone who looked similar to her - just like the corpse. Wig, dress and accent. If it's effective enough, no one will look further. Now, who would believe a magician girl to be the woman who supposedly passed away a few days ago?
Is it possible that the woman Amelia murdered was in fact Trucy Wright/Enigmar? If so, that would raise the number of kill-and-replace incidents to three in one trial, which is a lot. Not that it's a bad thing, I'm just commenting on the fact. Or did Trucy simply never exist in this AU, and were her sprites just used for a convenient appearance?