In my experience with this (Especially with Beam Turrets), when an 'officer' gets hit by your fire:
1) You're insta-wanted over 600 cr bounty.
2) The 'Green'/'Yellow' Officers on your radar STAY Green/Yellow for a few seconds more.
3) The Officer you shot, will instantly turn red, but not shoot at you.
4) About 10-30 seconds pass (An eternity in dogfights, and more than ample time to GTxO).
5) The Other officials will turn red, and they all start to target you.
6) About 2 to 4 more minutes, more officials may drop in to help slaughter you.
(I think officers basically go for the highest bounty in range first when it comes to multiples, then the closest bounty in range next)
In my opinion, I think that's pretty damn fair. The cops walk in on a two-person shootout not knowing who is in the wrong, you 'accidentially' shoot one of the officers in the leg. They see both parties as guilty, and open fire equally.
In my opinion, the only factor should be whoever has more positive faction with that Officer, should get more grace time, unless you hold SUPER HIGH RANK in that officer's faction, in which case, the officer lets you off with a 'Warning'.
There was talk in the game design discussions about how having a 'Well Maintained' ship in routine scans would have positive effects on your standing with Local System Officials. I think I'd like to see a combination of rank, standing, and system reputation have more effect on how officials react to you in these cases (Think 'Accident forgiveness'). And in some cases, you cannot be fined at all! "Oh, you shot the bad guy? I think we can look past that."
Until then, the Game Cops are treating everyone they don't know as the worst criminal in the universe out to get them, which I think is pretty much the Elite universe.
P.S. Take away the 'Oh we'll stop shooting so you can get the last shot' mechanic. Really?!?! This is 'Elite', right?!?!?