Are civilian review boards of any use, even where they do exist?
The cult mentality of police forces is hard to breach or change. They lead insular lives, for the most part, so it's almost impossible to expect anything but an us/them mentality taking root even among the most decent cops.
In the US particularly, where district attorneys are elected and judges are appointed by politicians constantly currying favour from the lowest common denominator voters, the public enables goon behaviour. The sensationalist media are echo chambers and promoters of law & order freaks. Police associations reinforce one another across state and county lines and now across international lines (Canada, for one).
The 9/11 "terrorism" hysteria continued the militarization begun with the crazy "war on drugs", the vicious killings carried out in home invasions in Iraq and Afghanistan are really no different from those in the US (chiefly the inner cities and mostly affecting persons of colour and the poor). Globalization in action, indeed.