Word at this hour is that the NAACP and various high-profile personages are calling for a federal prosecution of George Zimmerman for violating the civil rights of Trayvon Martin. This is a singularly bad idea and it ought to be dropped before it has a chance to grow legs.
When the practice of trying bad guys federally for civil rights violations became established in the 1960s, it was because the police and judicial systems of southern states were infected root and branch with racial bias and corruption, so that there was no chance of winning convictions in state courts. The Zimmerman case is in no way comparable to the state non-prosecutions of the killers of the three civil rights workers in Mississippi in 1964, or the frustrated prosecution of Byron De La Beckwith for killing Medgar Evers.
While the Zimmerman case produced a morally unsatisfying result, the trial cannot be said to have been fundamentally unfair. The problem was not with the conduct of the trial; the problem was with state laws in Florida that are fundamentally wrongheaded.
A federal civil rights prosecution of Zimmerman, while it might be technically allowable, would be seen as as gross overreach by federal authorities. It would diminish respect for the principle upon which such prosecutions were founded, and it would dissipate moral capital that can better be used in other fights.