Well...
In America, I'd probably not bother separating Police and Criminal. Functionally, they are the same thing, however, the level of knowledge that police need to do their jobs vs. the level of knowledge a defense lawyer needs are quite different. Regardless, they are the same laws and concepts.
You could go hugely broad and say "Litigation" vs "Dealmaking" (aka Transacational). That's probably not what you want.
You could also get rather specific--just look at any big firm's list of practice areas. For example,
http://www.klgates.com/services/xpuS...ST=ServiceList is particularly helpful, because it has larger categories that then are broken down even more.
Another example would be
http://www.perkinscoie.com/services/...grouplist.aspx.
Basically, it depends on how granular you want to get. I am a "consumer protection attorney." But my knowledge of American law is far broader, and most importantly, I'm trained to be able to figure out almost any new area of law (given time...how much time depends on the complexity of the field). This means I do a lot of contracts-like stuff, but breaking it down further is possible: I could specialize in unfair debt collection, or bankruptcy, or mortgage lawsuits...
It just depends on what you want.