Asari.
I think the fact they have Justicars proves just how loyal they are to justice (in general, yay for profiling!).
Of course, this would mean I'd have to be innocent to begin with. And that courts would work like they do for us.
But then again, Human might be best. As if I committed a crime against a human, then wouldn't the Alliance take control of the situation (as Shepard does for the Alliance over and over again in the first game).
The implications of some side missions (the one with that guy and his crazy Biotic compound or the L2 Biotics who wanted compensation, Garrus' personal quest in ME1) would imply that where the crime took place and who the crime victimized would dictate who had jurisdiction.
So, technically my choice would depend on who was judging. I'd want a lawyer to match the system (Asari for Asari or Citadel/Council trials, human for human, etc.). ^^