When I worked in the Provost Marshal's office every Thursday the JAG lawyers would come over and we'd go over case by case anything we thought might go to courts martial. We also had a cheat sheet gleaned from the blotter of all the DWI's and Drunk and Stupids we expected to be handled by Article 15's. That way when PVT Snuffy went to the JAG office after being read the Art. 15 by his commander, they'd already have the details.
The interesting thing was the Chief JAG officer had two rosters, one each Prosecution and Defense, and all the JAG were on each one. If your name was at the top of the roster for "Defense", you were defense for the next case. Then your name went to bottom of the Prosecution Roster. But we'd sit there and open each case file and go over everything with both JAG officers. Sometimes they'd be defense and the next case, they'd be prosecution. So they were constantly plying both sides. I think it made them much better attorneys.
Plus it was fun to watch them go from "Put the MF against the wall and shoot him.", on one case to; "He was on his way to choir practice at the orphanage, right after he left the abandon pet shelter, when evil befell him." on the next.
One thing that always impressed me about the CID agents I worked with, they worked just as hard to eliminate someone as a suspect as they did to find out who did it.
Oh, and the "overcharging" thing. Most it has to do with double jeopardy. You have to charge them with everything the first time. Apparently at some point in time prosecutors where charging people with X. And then wouldn't get a conviction, so they'd go back and charge them with Y and Z (lesser charges) and try to get a conviction that way. Now the courts (at least the military ones) want to see all the charges up front, so there's only one trial on all the charges.