i dont realy see a reason for a criminal to fight a cop in the VCPD unless he is cop hunting.. 
anyways, doing stuff like that are strictly against the rules of the server, since it is script abusing.
but only cop hunters will get into these kind of script abusing problems imo.
As Legend said, there is always excuse of clearing cop threat, and it's true
I'll give you an example, without the name of the cop (as I prefer him to be ashamed of himself when reading this lololoo)
Me, Morphine, Perry and few other guys are having party at IT HQ (I don't think I have to mention where that is, everyone knows)
A cop (lets call him cop1 as I won't defame him by calling him by nickname yet) comes in and starts shooting everyone without any warning (just typing /c sur once before)
He gets shot in the back, and starts running towards VCPD building...now you may call that cophunting (as I chased him) but we both know that is bullshit..if you think this is 'cophunting' then you're clearly wrong - I can RP a criminal the way I want, either if he's raged and not careful at all or very pussy, trying to avoid shooting to cops...you can tell me that chasing a cop and shooting at him is 'not RP omg cophunting omg', but indeed, it's clearing the threat. If I would not chase him down (or at least try to) he would most probably get some buddies, kevlars, weapons, and come back.
Anyways the point is, I'm chasing the cop,
cop gets knocked down by hail of bullets from other's shotguns...what is he doing? Meh, fuck it, he takes some extacy and takes another kevlar whilst knocked down, after his HP is like 20 he restocks again. I reported the case to admin who was online, but I was told it isn't any 'script abusing', and no consequences were taken.. The cop was restocking till he could by clear luck kill the criminals one by one.
Now you see Dani, I know you're a good cop, so if a script like that would be implemented, I don't think it would do anything to real cops who roleplay, not just 'DM legally'. I mean Dani, you don't come into VCPD restocking 100 times and hunting criminals there, do you? a 30 seconds limitation wouldn't do you nothing, as mostly cops restock only when they are hurt and specially get back into VCPD station just to do that.
I try to stay out of the VCPD stations as mostly as possible...but I will not let cops to just shoot me two times or three, nearly die and go with 20 HP to restock, instead I will try to hunt him down (unlesss the situation doesn't let me to) and don't tell me that's 'cophunting', please, I don't want to laugh :P If I will let the cop restock, he will came back just like nothing would happen to him, and try to hunt me down again. It's kinda basic logic.
I know criminals should run mostly, but as I said, criminals don't have to RP only one behaving - aka running, like most cops think. Try to enter a building full of criminals fully armed, when being a lone wolf, IRL - I don't think you would think they will just run away, would you?