Gater Communities; Protected Communities; Neighborhood Watch; and Warlords.

You can tell that a police function has failed when communities need to protect themselves. It is a vote of "no confidence" in the law enforcement function of a city or state when private security guards are hired, neighborhoods create watches or people turn to home-grown militias to enforce laws and defend themselves from marauders. This is the case in Rio as well as many other areas of the world.

From Belmont Club:

One way to recognize a failing state is to examine the extent to which its cities are subdividing into gated communities. ...

The Poor Man's gated community is secured by creating a neighborhood watch, often manned by former military men, as happens in Baghdad. The Rio militias that the Washington Post describes are just simply one way poor people pull up the drawbridge around their patch of turf. They chose a local warlord and in some respects transfer allegiance to him, while maintaining a separate relationship to a High King in the capitol.

...It is often forgotten that the Dark Ages were also the heyday of multiculturalism. Each valley held its petty lord and it was possible for places separated only by a few miles to speak totally different languages. But it can't happen again, can it?