March 26: This post has been updated to reflect the latest in the ongoing investigation of the shooting, and corrected.

"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.

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."

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.

If self-defense is invoked in Florida, the person is immune from criminal or civil prosecution.

In the Martin case, the local police chief has said that they did not arrest the shooter, George Zimmerman, because their initial investigation supported his self-defense claim, and that they were therefore prohibited from making an arrest or prosecution. (The police report on the shooting refers to it as an "unnecessary killing to prevent unlawful act.")

The police chief has since temporarily stepped down, after a vote of no-confidence from the city. The case is being investigated by the Department of Justice and a Florida state attorney. A grand jury will convene on April 10 to decide whether charges can be brought against Zimmerman.

Zimmerman's lawyer said in an interview with ABC News that Zimmerman will be protected under Florida's self-defense law.

In Florida, a homicide case can be thrown out by a judge before trial because the defendant successfully invokes self-defense. The burden is on the prosecution to disprove the claim in order to bring charges, rather than do so in the trial. The Florida state attorney leading the prosecution told ABC news that the self-defense law means it is "more difficult than a normal criminal case" to bring charges.

Florida is not alone in its expansive definition of self-defense. Twenty-four other states now allow people to stand their ground. Most of these laws were passed after Florida's. (Some states never had a duty to retreat to begin with.)

Here's a rundown of the states with laws mirroring the one in Florida, where there's no duty to retreat in public places and where, in most cases, self-defense claims have some degree of immunity in court. (The specifics of what kind of immunity, and when the burden of proof lies on the prosecution, vary from state to state.)

Many of the laws were originally advocated as a way to address domestic abuse cases — how could a battered wife retreat if she was attacked in her own home? Such legislation also has been recently pushed by the National Rifle Association and other gun-rights groups.

Click on the state to see its law.

Alabama

Arizona

Georgia

Idaho

Illinois (The law does not include a duty to retreat, which courts have interpreted as a right to expansive self-defense.)

Indiana

Kansas

Kentucky

Louisiana

Michigan

Mississippi

Montana

Nevada

New Hampshire

North Carolina

Oklahoma

Oregon (Also does not include a duty to retreat.)

South Carolina

South Dakota

Tennessee

Texas

Utah

Washington (Also does not include a duty to retreat.)

West Virginia

Sources: Legal Community Against Violence; National District Attorney’s Association; Association of Prosecuting Attorneys.

Correction: This post has been corrected to include New Hampshire in the list of states with laws that are similar to Florida's.