> Not in the USA, they don't. Not as long as the cops in question don't know for a FACT that their behavior violates established law - even if it DOES violate established law, they aren't held accountable unless a previous court case established precedent under almost the EXACT SAME CIRCUMSTANCES.

This only applies to civil liability; criminal prosecution of unreasonable use of force is not affected by QI, though there are other problems with that.