Calling the killing of Florida teenager Trayvon Martin a "tragic, unnecessary shooting," Attorney General Eric Holder on Monday repeated the Justice Department's intention to take a fresh look at the case and evaluate whether federal prosecutors could bring charges of their own. A decision is very likely months away. But several legal experts say it would be surprising if the federal government filed a criminal case against George Zimmerman. "Based on what's in the public eye, it would be very difficult to get a conviction in this case," said Samuel Bagenstos, a former top official in the Justice Department's Civil Rights Division. If the government were to bring a criminal case, it would most likely invoke the four-year old federal hate crime statute named for Matthew Shepard and James Byrd, both of whom were killed in vicious bias attacks. Part of the federal law is a provision making it a crime to cause "bodily injury to any person because of the actual or perceived race" of the victim.