Bloody hell!
BACK TO THE FEATURED DISCUSSION -
I think that the Legal Decision Maker (Judge) should be the head of his own pseudo-squad of investigators, just as the Chief Doctor is. In this fashion, you can split it from anything else, or you can designate the Hammerer as Judge without a squad for a Judge Dredd style systejm, or the Expedition Leader as Judge for autocracies, or the Militia Leader and his squad as Judge+squad for military Juntas, or hell, even assign a total random and a bunch of randomly selected mooks as judge+squad for a less consolidated legal system. This would cover a massive array of possible legal systems (religious, military, noble, etc) with very little effort. Obviously squads are good for investigating, as ZM5 said, because more bodies are useful, but it also introduces more risk and requires more dwarf-hours.
I would be in favour of the player assigning this role as any other, and potentially having a few levels of judge, just as counts, dukes, barons etc do, so your judge might start off as just that, then the next highest position once a certain threshold is reached would become a High Judge, and finally the Supreme Judge. Again, all of these could be rolled into various other positions, so the Monarch might also be Supreme Judge, while at your colony of zealots the position of High Judge is given to a priest, and at one of your outposts, the Expedition Leader is Judge. The outpost judge makes local legal decisions but can be overruled by your High Judge, and both of those can be overruled by the Monarch-Supreme Judge at the top.