Anger At Injustice: What Is The Best Response To The Van Dyke Sentencing?

The entire nation, indeed the world, has been made aware through a shocking dash cam video that in 2014 a seventeen year old black youth, Laquan McDonald, was literally gunned down while walking away from a police officer, Jason Van Dyke who shot him sixteen times.  The verdict of guilty of second degree murder and 16 counts of aggravated battery was historic in that no white police officer had ever been found guilty of a crime in the on duty shooting of a black youth. Yet, citizens are outraged that the sentence of 81 months given to Van Dyke was little more than a slap on the wrist. What real power do citizens have that they need to exercise in order to prevent homicides committed by police - the individuals hired through tax dollars to serve and protect them?