SANFORD, Fla. (AP) — George Zimmerman’s lead attorney will be walking a fine line as he tries to convince jurors that his client didn’t murder Trayvon Martin: He needs to show why Zimmerman felt threatened by the African-American teenager while avoiding the appearance that either he or his client is racist.Because there is no dispute that Zimmerman shot Martin, 17, during a fight on a rainy night in February 2012, Mark O’Mara must convince the jury that Zimmerman pulled his 9 mm handgun and fired a bullet into the Miami-area high school student’s chest because he feared for his life and that the fear was caused by Martin’s actions, not his race.Jury selection begins Monday in the second-degree murder trial, which is expected to last about six weeks. Martin’s killing drew worldwide attention as it sparked a national debate about race, equal justice under the law and gun control. If convicted, Zimmerman, who identifies himself as Hispanic, could get a life sentence.Under Florida law, Zimmerman, 29, could lawfully shoot Martin in self-defense if it was necessary to prevent death or great bodily harm.O’Mara has to be careful how he characterizes Martin, said Randy McClean, an Orlando-area defense attorney.