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"Stand Your Ground," "Shoot First," "Make My Day" state laws—asserting an expansive right to self-defense—have come into focus after last month's killing of 17-year-old Trayvon Martin.

While local prosecutors have not arrested the shooter, George Zimmerman, the case is now being investigated by the Department of Justice and a Florida state attorney. It's not clear whether Florida's self-defense law will be applied in the case. (The police report on the shooting refers to it as an "unnecessary killing to prevent unlawful act.")

Still, in not arresting Zimmerman, local officials have pointed to Florida's wide definition of self-defense. In 2005, Florida became the first state to explicitly expand a person's right to use deadly force for self-defense. Deadly force is justified if a person is gravely threatened in the home or "any other place where he or she has a right to be."

In Florida, once self-defense is invoked, the burden is on the prosecution to disprove the claim.

Most states have long allowed the use of reasonable force, sometimes including deadly force, to protect oneself inside one's home—the so-called Castle Doctrine. Outside the home, people generally still have a "duty to retreat" from an attacker, if possible, to avoid confrontation. In other words, if you can get away and you shoot anyway, you can be prosecuted. In Florida, there is no duty to retreat. You can "stand your ground" outside your home, too.