The law affords people enormous leeway to use deadly force if they feel their life is seriously endangered. Sonner said Zimmerman felt "one of them was going to die that night," when he pulled the trigger.
Corey, a veteran prosecutor known for her zealous defense of victims rights was hand-picked by Florida Gov. Rick Scott for the job. But she faces other challenges in the case.
While in life Trayvon Martin was barely 17, when it comes to justifiable homicide his size -- about 6-foot-3 and 150 pounds -- makes him an adult in death.
Zimmerman, 28, is 5-foot-9 and weighs well over 200 pounds.
But with the Department of Justice and the FBI investigating this case as a possible hate crime, Corey might want to pursue that as well.
"So it would depend on which charge if any we're able to file," she said. "Before we would be able to determine, one, if this is a hate crime, and two, whether or not that would enhance the crime."
Corey's team is now reinvestigating a case that the Sanford Police Department is accused of bungling. Possible police missteps include failing to administer a toxicology exam on Zimmerman, not impounding his car, and failing to contact key witnesses -- like Martin's girlfriend, who was talking to the teen by cell phone and heard most of the scuffle with Zimmerman unfold.
ABC News has learned there is tremendous pressure from local and state authorities for an arrest.
Corey said parts of the investigation might only take a few more days to complete but charges, if they ever come, could be weeks away.