George Zimmerman in his April 11 booking photo: The neighborhood watch volunteer is expected to plead not guilty to second-degree murder.

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even weeks after he admittedly shot and killed 17-year-old Trayvon Martin in a Sanford, Fla., gated community, and about three weeks after the shooting hit the national news with a vengeance, neighborhood watch volunteer George Zimmerman was arrested on Wednesday and charged with second-degree murder. For his safety, Zimmerman is being held at an undisclosed Florida jail. Angela Corey, the Florida state attorney who was assigned to the case as a special prosecutor after Florida's governor lost confidence in local law enforcement, announced the charges at a press conference in Jacksonville. Here's a closer look at the charges, the applicable laws, and what happens next.

What exactly is the charge Zimmerman faces?
Corey is prosecuting Zimmerman on one count of second-degree murder, alleging that he committed an unpremeditated "act imminently dangerous to another, and evincing a depraved mind regardless of human life." Typically, second-degree murder requires an "evil, hateful, or spiteful" intent, while the lesser charge of manslaughter means the shooter was merely reckless. Zimmerman's new lawyer, Mark O'Mara, says his client will plead not guilty.

Why murder instead of manslaughter?
Many defense attorneys were surprised that Corey opted for the tougher charge. Their conclusion: "Corey and her team of prosecutors must know something that the rest of us don't," says Dan Sullivan in the Tampa Bay Times. Legal experts say the jury can still choose to convict Zimmerman of manslaughter if they don't think he's guilty of murder, or Zimmerman can negotiate a lesser charge as part of a plea agreement.

How much jail time could Zimmerman get?
If convicted of murder, Zimmerman faces a mandatory minimum of 25 years in jail, and a maximum sentence of life behind bars. Manslaughter carries a maximum sentence of 30 years in jail.

What happens now that he has been charged?
Zimmerman will be arraigned Thursday, and can ask to be released on bail. It's possible that the 28-year-old could be granted bail because he has proved that he's not a flight risk. But if he does get bail, he will almost surely remain under protective custody. Zimmerman's legal team will also likely ask the judge to grant their client immunity from prosecution under Florida's "stand your ground" law, which gives legal gun carriers wide latitude to shoot people they reasonably fear will kill them or cause them grievous bodily harm. If the judge accepts the request, Zimmerman walks; if he dismisses it, the case will go before a jury.

Will Florida's gun law protect Zimmerman?
"To mix metaphors, stand your ground is no slam dunk," says Reuters in a legal analysis. To win immunity under the law, the burden of proof is on the defendant, and few meet it to a judge's satisfaction, criminal defense attorney Ralph Behr tells Reuters. "Most judges, I think, are comfortable letting the adversarial system play out before a jury rather than make decisions themselves." During Wednesday's press conference, Corey told reporters, "If stand your ground is an issue, we'll fight it."

What will most likely determine the outcome of the case?
The key question is probably whether Zimmerman or Martin was the aggressor in their scuffle — in other words, did Zimmerman fire in self-defense? But most legal experts agree that it will come down to forensic evidence, and not unreliable, contradictory witness accounts. "We are going to find out that the prosecution has one or more pieces of physical evidence that contradicts Zimmerman's story," like autopsy results or ballistics tests, predicts Miami defense attorney H.T. Smith. Corey must believe she has the goods, says Gabriel J. Chin at CNN. But "because the critical facts of the case have not been revealed, it is impossible to predict how the case will fare when tested in the crucible of the courtroom."

Sources: ABC News, AP, Bloomberg, Christian Science Monitor, CNN, Emptywheel, Reuters, Tampa Bay Times, Telegraph, Washington Post, USA Today