I'm not entirely sure but think that this would fit better in the Dark Milennium boards.
Anyways, it looks very interesting. Dividing them into such categories depends on the number of players and what kind of warband they will use. The good guys should have a reason to also be at eachother's throats, otherwise they would form a block agains the other players, while it is much more fun if they are all trying to kill eachother.
To this end you could give each warband an individual objective, such as burning the evidence, hiding it again, getting rid of anyone who knows about it or even someone who wants to bring the truth out(a real idealist)