Absolute power corrupts absolutely.  The police has absolute power over a citizen in a confrontation. Which is why some members of the police force are corrupted by such power.  

The solution is to avoid hiring bad apples into the police force.  

And bad apples in the police force have to be monitored and either be fired or be assigned to a desk job when citizen complaints - unjustified or justified - reaches a maximum limit.

That's all there is to it.  Bad Apples in the Police Force, policemen who have tasted absolute power over a citizen and succumbed to human tendency to abuse such power.  

The police have certain procedures to protect themselves from the criminal elements.  It is this procedure that is abused over innocent civilian.