Hey David...
I have a JVC GR-DZ7U Mini-DV camera that works decent in low light, is 2 mega pixel effective resolution, and doubles as a digital camera. Its a little on the pricey side for you ~$700 or so. It has the flip out screen on the side so its easy to tape with. I would recommend using Mini-DV tapes as they are cheap and you can catalog the tapes easily, packs of Mini-DV tapes can be had for cheap and will hold an hour a piece.
The only drawback on mine and something you want to think about is having the camera on charge through a 12v outlet or lighter outlet in the squad car. My JVC has a proprietary charger (i.e. goofy plug you can't get at Best Buy or Radio Shack) cable so you'll need to check any individual model to see if it will charge direct from 12v without some stupid adapter.
This camera is about 2 lbs or so and could easily be carried in a tactical bag and take a little knocking around.
http://www.pcmag.com/article2/0,1759,1674786,00.asp
The review says the menus are not so easy to navigate which is true, but you can hit the power switch and be taping in 3-5 seconds.
Steer clear of cameras in this price range that have "optical" image stabilization. They blow.