Less than a year into the post-Obama milieu, yet another major police shooting trial—the Jason Stockley case in St. Louis—produced a widely denounced verdict that reminds us how difficult it is to hold police officers accountable when they murder African Americans. Then-St. Louis police officer Stockley shot and killed Anthony Lamar Smith as he fled off in a vehicle. This happened in 2011, almost three years before the police killing of Michael Brown in the St. Louis suburb of Ferguson. Which me…