At dusk last Monday, Norma Corona Sapienz, 38, president of the State Commission for the Defense of Human Rights in Culiacan, on Mexico's Pacific Coast, was driving home from work when three men in a pickup blocked her path. She tried to flee on foot. Suddenly gunfire rang out, and five bullets tore through the prominent attorney's back, killing her instantly.
The assassination was hardly unusual. Drug trafficking has led to a spate of killings. However, in Mexico much of the violence is the work of corrupt police officials, who often operate under the guise of stepped-up narcotics enforcement. Despite President...