(AP) — Legal experts say it won’t be easy for the Justice Department to mount a federal civil rights case against George Zimmerman after a Florida jury acquitted him of state charges in the shooting death of Trayvon Martin.

One observer, former U.S. Attorney Alan Vinegrad, says the department would have to show, among other things, that the attack was unjustified and racially motivated.

Those are some of the same challenges that complicated the unsuccessful state case.

The Justice Department says it’s reviewing evidence to determine whether criminal civil rights charges are warranted. It had opened an investigation into Martin’s death last year but stepped aside to allow the state prosecution to proceed.

The NAACP and other groups have called on the Justice Department to open a civil rights case against Zimmerman.