MIAMI — Nearly three weeks after an unarmed teenager was killed in a small city north of Orlando, stirring an outcry, a few indisputable facts remain: the teenager, who was black, was carrying nothing but a bag of Skittles, some money and a can of iced tea when he was shot. The neighborhood crime watch volunteer who got out of his car and shot him is white and Hispanic. He has not been arrested and is claiming self-defense.

Beyond that, however, little is clear about the Feb. 26 shooting death of Trayvon Martin, 17.

As criticism of the police investigation mounts, so too do the calls for swift action in a case with heavy racial overtones. Protests grow larger each week, and lawyers for the family are now asking the Department of Justice to intervene. The case also brings into sharp focus Florida’s self-defense laws, which give people who feel threatened greater latitude in defending themselves than most states.

The police in of Sanford, where the shooting took place, are not revealing details of the investigation. Late Friday night, after weeks of pressure, the police played the 911 calls in the case for the family and gave copies to the news media. On the recordings, one shot, an apparent warning or miss, is heard, followed by a voice begging or pleading, and a cry. A second shot is then heard, and the pleading stops.

“It is so clear that this was a 17-year-old boy pleading for his life, and someone shot him in cold blood,” said Natalie Jackson, one of the Martin family lawyers.