Crowded with Washington-bound commuters, the Track 5 platform beneath 30th Street Station was swept by a cold wind as Ron Levine stamped his feet and blew into his hands to stay warm.

On this unusually icy November day last year, Levine, a prominent white-collar defense lawyer and a former prosecutor in the U.S. Attorney's Office in Philadelphia, and his colleague, Abe Rein, were on their way to the nation's capital. There, they would meet with other lawyers to fine-tune arguments in a Supreme Court case.

Their client had been sentenced to federal prison for threatening to kill his wife and an FBI agent in rap lyrics posted on Facebook, and he was claiming First Amendment protection.

Their mission? Persuade the highest court in the land to overturn the conviction.

It was the first time one of Levine's cases had gone all the way to the Supreme Court. But if Levine was awestruck that his case was chosen from among the thousands that each year vie for a Supreme Court review, he gave no hint of it.

While he and Rein waited for Amtrak's 9:37 Northeast regional train to arrive, the Oxford University and Harvard Law School graduate coolly tapped away on his iPhone.

"This isn't the capstone of my career," Levine remarked, "but it isn't a routine matter either."

Some time in the coming weeks, the Supreme Court is expected to render a decision, and when it does, it won't be only Levine and Rein paying close attention. With its potential for defining when the government can prosecute for violent statements on the Internet, the case has become one of the most closely watched of the current term.

Dozens of interest groups have sought to weigh in with friend-of-the-court briefs. They range from the Anti-Defamation League, which is urging the court to uphold the conviction, arguing that Internet bullying will otherwise spread, to People for the Ethical Treatment of Animals, which worries its confrontational style of protest might be more easily prosecuted if the conviction stands.

"This case has generated interest not only because of the underlying legal issues, but because the communications took place on social media, which is how more and more people interact," said Washington appellate lawyer John Elwood, who has been working with Levine and Rein on the appeal. "That makes the issue legally fresh and culturally novel."

Unlike same-sex marriage or the emotional litigation over President Obama's health-care plan, the majority of cases heard by the Supreme Court make no significant news. Often as not they involve disputes over obscure and highly technical subjects such as patent law or the tax code. They may have enormous bottom-line impact for business, but they do little to stir popular passion.

Not so Levine's Supreme Court appeal. On Oct. 20, 2011, a federal jury convicted his client, Anthony Elonis, a onetime operations manager at Dorney Park & Wildwater Kingdom amusement park in Allentown, of violating federal law by using the Internet to threaten to kill his wife and an FBI agent in a series of Facebook posts.

At his trial, Elonis claimed that he never intended to threaten anyone and that his postings were a form of therapy.

The defendant

It would be hard to find a more unappealing protagonist than Elonis. His world began to fall apart in the spring of 2010, when his wife left him, taking their two children. His supervisors at Dorney Park sent him home from work after they heard and saw him crying "hysterically" with his head down on his desk.

Around the same time, a female coworker filed five sexual-harassment complaints against him.

On Oct. 17, 2010, the 28-year-old Elonis posted a picture on Facebook. It showed Elonis and the woman who had made the sexual-harassment complaints dressed in costumes the staff use for the park's annual Halloween Haunt. Elonis held a fake knife to the woman's throat. The photograph initially was intended as a park promotional photo, but on Facebook Elonis added the caption: "I wish."

He was fired a short time later.

Thus began a period of increasingly agitated and hostile postings, which Elonis occasionally described as artistic musings and which from time to time were accompanied by disclaimers that his words were not to be taken seriously.

He even had a rap pseudonym - Tone Dougie.

After his firing, Elonis posted a reference to the coming Halloween Haunt:

"Moles! Didn't I tell y'all I had several? Y'all sayin' I had access to keys for all the [expletive] gates. That I have sinister plans for all my friends and must have taken home a couple. Y'all think it is too dark and foggy to secure your facility from a man as made [sic] as me? . . . Whoever thought the Halloween haunt could be so [expletive] scary?"

On Nov. 16 that year, FBI agent Denise Stevens, who had begun monitoring Elonis' site, read this Elonis posting:

"That's it, I've about had enough. I'm checking out and making a name for myself. Enough elementary schools in a ten mile radius to initiate the most heinous shooting ever imagined.

"And hell hath no fury like a crazy man in a Kindergarten class. The only question is . . . which one?"

That post so alarmed Stevens that she and another agent went to visit Elonis, who by then was living at his parents' house in Bethlehem. Elonis came to the door, but declined to speak with Stevens.

Later that day, he posted this on Facebook:

"Little Agent Lady You know your [expletive] is ridiculous When you have the FBI knocking at yo' door Little Agent lady stood so close Took all the strength I had not to turn the bitch ghost Pull my knife, flick my wrist, and slit her throat Leave her bleedin from her jugular in the arms of her partner.. . ."

One week later, the FBI arrested Elonis.

Different kind of case

Soft-spoken and precise, Levine is a sought-after defense lawyer whose clients typically include well-heeled executives and moneyed corporations, not indigent criminals accused of threatening to kill their wives in rap lyrics on Facebook.

He did his undergraduate work at the Wharton School of the University of Pennsylvania and then spent two years at Oxford, where hethi did graduate work in sociology. After law school and a clerkship with the federal district court in Philadelphia, Levine spent 17 years as an assistant U.S. attorney in the city, rising to become the head of the criminal division before founding the white-collar defense practice at Post & Schell in Center City. One reason clients seek him out is his deep familiarity with the way the Justice Department works and how prosecutors think - qualities that help head off indictments.

Levine is also among a pool of local lawyers who represent indigent clients at reduced rates, and that is how he came to represent Elonis.

Levine, 61, says it didn't take much convincing when Lawrence Stengel, the federal istrict judge who presided over the Elonis trial, called and asked if he would represent Elonis.

"The issue isn't so much my belief in guilt or innocence; the issue is, did the government in a fair way bring charges and prove charges according to the law?" Levine said.

Levine drafted Rein to assist in the case in part because Rein had spent several years running a Web design company before law school, and Levine reasoned that his deep familiarity with the Web would be an asset. He and Rein first tried to overturn Elonis' conviction with an appeal to the U.S. Court of Appeals for the Third Circuit. They argued that Stengel's instructions to the jury, though in keeping with Third Circuit precedent, erred by failing to afford their client full First Amendment protection.

The Third Circuit Court upheld the conviction, but a few weeks later, Levine got a call from the University of Virginia law school's Supreme Court litigation clinic.

Students there had been combing through recent appellate decisions, and it seemed that the issues raised in the Elonis case were ripe for Supreme Court review.

The students offered to help in preparing a petition for certiorari, a request that the Supreme Court hear the case. Moreover, Elwood, an appellate lawyer at the firm of Vinson & Elkins and a lecturer at Virginia with long experience practicing before the Supreme Court, would be available to make oral arguments.

Levine accepted the offer.

The case turns on an obscure but critical question in First Amendment law: When can a person be charged with a crime for making threatening statements, if the person claims no threat was intended? Should prosecutors be required to prove such intent and show the accused engaged in what the law calls a "true threat"? The Supreme Court has had little to say directly about the issue, and appellate courts directly below it are divided.

That the threats occurred on Facebook adds another dimension, legal experts say. Because social media have such wide reach, it is often the case that a person receiving a communication in a chat room or on Facebook will know nothing about the sender, greatly increasing the likelihood of misinterpretation. Under those circumstances, a message intended as a joke might be deemed, incorrectly, a threat.

From the start, the challenge for Levine, Elwood, and Rein was not about airbrushing Elonis' problematic image. Rather, their focus was on whether the trial judge had correctly defined the alleged crime to the jury.

Rap artists, political activists, and even college editorial writers have been prosecuted under threat statutes, which date back to the 18th century and beyond.

But the Supreme Court has weighed in only infrequently. The court issued a key ruling in 1969 in the case of Watts v. United States, in which a young man about to be drafted said at an antiwar rally that he would "grab a gun and shoot the president" if drafted.

Robert Watts was prosecuted and convicted, but the Supreme Court overturned the conviction, saying the circumstances - it was a political rally, and the audience laughed at Watts' remarks - made clear he was engaging in political hyperbole.

Most recently, the court ruled in Virginia v. Black in 2003 that a Virginia statute making it a crime to threaten someone with a Ku Klux Klan-style cross-burning was unconstitutional. The court said the law failed to take into account whether the threat was a "serious expression of an intent to commit an act of unlawful violence."

The court said that if the Virginia law were upheld, merely using a burning cross in a film to depict KKK activity could be prosecuted.

Since the Black decision, federal circuit courts have issued differing interpretations. Some, like the U.S. Court of Appeals for the Third Circuit, have found prosecutors must show only that a reasonable person would have deemed the communication threatening, a concept known as the "objective standard."

Others, such as the Ninth Circuit Court in California, have imposed a more stringent test, requiring prosecutors to show the accused intended to threaten bodily harm. At the end of Elonis' criminal trial in October 2011, Stengel instructed the jury to use the objective standard.

After deliberating for two hours, the jury convicted Elonis.

What is a threat?

On Dec. 1, the day of oral arguments, Elwood parried questions from the justices during the 30 minutes each side had to try to persuade the court. Levine, Rein, and Daniel Ortiz, a law professor at Virginia who also has been working on the case, quietly conferred with Elwood while Deputy U.S. Solicitor General Michael Dreeben made the government's argument and Elwood readied his rebuttal.

The justices, as they are prone to do, repeatedly interrupted.

Justice Samuel A. Alito Jr. wanted to know how anyone might be convicted of making a threat if the accused could claim the threatening language was not serious.

"This sounds like a road map for threatening a spouse and getting away with it," Alito said in an exchange with Elwood.

Chief Justice John G. Roberts Jr. asked whether, if the government's case were upheld, rap singer Eminem, who also wrote about killing his wife, should be arrested.

Meanwhile, Justice Sonia Sotomayor seemed troubled by the government's position, which she suggested might curtail free-speech rights.

The line of questioning suggested the justices were troubled by the potential harm of threatening language on social media, but also wary of a ruling that might undermine free-speech rights.

As Levine and his team left the court, and then posed for pictures on the marble steps outside, they could only wonder how the case would play out.