Zimmerman, a former neighborhood watch volunteer, was acquitted of second-degree murder in July 2013. He has said he shot Martin in self-defense during a confrontation inside a gated community in Sanford, Florida.
The case created a national conversation about race and self-defense gun laws. Martin, who was unarmed when he was killed, was black. The teen's relatives have accused Zimmerman of starting the fight and racially profiling Martin.