The past year has seen a series of high-profile cases in which police have been accused of using unnecessary and even lethal force, especially against black suspects.

Not all of these incidents have proven to be what they first appeared, as the apparently justifiable shooting of Michael Brown in Ferguson demonstrates. But some of the cases seem very clear-cut. Americans of all races and political stripes reacted with outrage at the videotaped choke-hold that led to the death of Eric Garner in Staten Island. And there is almost no racial divide in public opinion regarding the outrageous videotaped police shooting of the unarmed, fleeing Walter Scott in South Carolina.