After a rough two weeks for the prosecution, George Zimmerman's defense lawyers have now taken control of the trial. The job of the defense's case (which is always preceded by the State's) is typically to shoot holes in the prosecution's argument—though, in this case, several of the prosecution's witnesses have done that all by themselves.
The key question facing the court's decision is now: was it Zimmerman or Martin screaming and calling for help in the infamous recorded 911 call? Zimmerman's defense team has opened with that very question, inviting several witnesses to the stand who claim that it was Zimmerman's voice—or at least, as some of the case's lead officials told the jury, not Martin's.
Lead investigator Christopher Serino recalled that Tracy Martin, father of Trayvon, didn't seem to recognize Trayvon's voice when played the recording. "He looked away, and under his breath—as I interpreted it—said, 'No,'" Serino told the court.
Both Serino and officer Doris Singleton have testified before, during the prosecution's case—and, under the scrutiny of the defense, claimed absolutely that Tracy Martin didn't recognize the voice saying 'Help.' "There was no doubt that he was telling us that it wasn't his son," added Singleton.
Zimmerman's family and friends have insisted the same thing. This point is perhaps the most critical of the trial because, if proven one way or another, will strongly suggest which man attacked the other first—and, by extension, whether Zimmerman is telling the truth. However, voice analyst Dr. Hirotaka Nakasone has testified that it's impossible to conclusively tell from playback whose voice it is. The mothers of both men have sworn under oath that it's their son.
The defense isn't striving to prove that Zimmerman didn't shoot Martin; if they can convince the jury that there is "reasonable doubt" against the charge of second-degree murder, Zimmerman will likely face much less severe penalties—or even walk free. Analysts have predicted that the latter scenario is not unlikely.