The killing of Trayvon Martin incited outrage and protest marches across the country. He was shot on the evening of Feb. 26 as he returned from buying Skittles and iced tea at a 7-Eleven, bound for the home in a gated community in Sanford, a small city just north of Orlando, where he and his father were guests.

Mr. Zimmerman, the founder of the local neighborhood watch, called 911 that evening to report that Mr. Martin looked like “a real suspicious guy.” Some questioned whether Mr. Martin attracted Mr. Zimmerman’s attention simply because he was black. Others were outraged by the slow reaction of the local police and prosecutors, who did not immediately arrest and charge Mr. Zimmerman, saying that Florida’s self-defense law could make it difficult to prove a criminal case against him.

President Obama weighed in on the case at one point, saying, “If I had a son, he’d look like Trayvon.” After television commentators suggested that Mr. Martin might have looked suspicious because he was wearing a hooded sweatshirt, people around the country began donning them in solidarity. LeBron James and other members of the Miami Heat basketball team posed in them for a photograph they posted on Twitter. Representative Bobby L. Rush, Democrat of Illinois, even wore one on the floor of the House, saying “Just because someone wears a hoodie does not make them a hoodlum.”

The case drew attention to Florida’s Stand Your Ground Law, which was enacted seven years ago after lobbying by the National Rifle Association, over the objections of many law enforcement officials. The law gives the benefit of the doubt to people who claim self-defense, even if they are not in their homes; it says that people who feel that they are in danger do not need to retreat, even if it would seem reasonable to do so.