Florida's second sensational, race-tinged murder trial in less than a year is underway. Michael Dunn, a white, 47-year-old software developer, shot and killed Jordan Davis , a 17-year-old African American, as the teen sat in an SUV with three friends. Charged with first-degree murder, Dunn is pleading self-defense under Florida's controversial Stand Your Ground law. He contends that he argued with the teens (over what a witness says he called their " thug music ") and fired on them after he claims he saw Davis brandish a shotgun. Police found no gun at the scene, and witnesses say Davis never had one.