For weeks, online and on the streets, people called for the arrest of the man who fatally shot an unarmed black 17-year-old, Trayvon Martin. To them the shooting constituted what they no doubt saw as murder, despite the speculations of many legal experts that, at most, the man, George Zimmerman, might be charged with manslaughter, a less serious felony. Then last week, after he was finally arrested, news outlets across the country spread the word, emphasizing the second-degree-murder charge and reporting that if he is convicted, Zimmerman faces life in prison under Florida law.

Technically, that is true, but don't count on it. While murder requires proof that Zimmerman acted with "depraved" indifference to human life, manslaughter requires only proof that Zimmerman was reckless or negligent.

As the state case sorts itself out, don't get your hopes up for a federal prosecution. U.S. Attorney General Eric Holder, obviously trying to pave the way for what might be a not-so-popular outcome, said during a press conference last week: "For a federal hate crime, we have to prove the highest standard in the law. You know, something that was reckless, that was negligent, does not meet that standard. We have to show that there was specific intent to do the crime with the requisite state of mind."

Expect this to be a long, drawn-out case, challenging not only our attention span but also the controversial "Stand your ground" law that could be the linchpin of Zimmerman's defense. It has usually worked when invoked, according to the Tampa Bay Times. Under the law, adopted in 2005, a person has no obligation to retreat from a situation where he reasonably thinks his life is in danger. He can shoot; authorities ask questions later.

The anticipated pretrial "Stand your ground" hearing would be months off but could result in a judge setting Zimmerman free because he acted in self-defense. Failing that, there could be a plea bargain agreement before trial, not unusual in Florida murder cases. Or a jury could decide to convict him not of murder but rather of manslaughter. Murder carries a sentence of life; manslaughter, 15 years.