Tomorrow in florida, they'll start the process of selecting the jury of one of the most case, george zimmer. Sparks were flying in the courtroom already this weekend. Here's abc's matt gutman. Reporter: Tomorrow, george zimmerman is set to begin. At issue the past week, who was howling on this 911 call. This is the worst possible forensic example. Reporter: A single gunshot killed 17-year-old trayvon martin and now zimmerman faces a second-degree murder charge. The defense, they were zimmerman's. The state and defense agree on one thing, whoever howled was the victim in the fight. Since that night, zimmerman has been fighting that he shot martin in self-defense. Starting monday, some 500 residents will be questioned and prodded about their views on race, guns and the media hoopla around the trial. Experts tell abc news, whiting the 500 jury to 12 people could take weeks. The trial comes 16 months after that single bullet launched these protests. High school walkouts, even grabbed the attention of the president. My main message is to the parents of trayvon martin, you know, if I had a son he would like trayvon martin. This is going to be a major trial in america. It really kicks off tomorrow.