New York Times

WASHINGTON — As the Supreme Court on Monday tried to puzzle out what threats may be prosecuted as crimes, Chief Justice John G. Roberts Jr. cited an unlikely source: the rapper Eminem.

Treading gingerly, the chief justice quoted vivid lyrics from “ ’97 Bonnie and Clyde,” in which Eminem seems to threaten to drown his wife.

“Could that be prosecuted?” Chief Justice Roberts asked Michael R. Dreeben, a government lawyer.

Mr. Dreeben said no and started to say something about context. Chief Justice Roberts interrupted.

“Because Eminem said it instead of somebody else?” he asked.

The case before the justices also involved threatening rap lyrics arising from domestic troubles. They were posted on Facebook by Anthony Elonis, a Pennsylvania man who had adopted the rap persona Tone Dougie. The posts, long tirades in the form of rap lyrics, were punctuated by brutally violent language, most of it directed against his estranged wife.

He wrote that he would like to see a Halloween costume that included his wife’s “head on a stick.” He talked about “making a name for myself” with a school shooting, saying, “Hell hath no fury like a crazy man in a kindergarten class.” He fantasized about killing an F.B.I. agent.

Some of the posts contained disclaimers or indications that they aspired to be art or therapy. At Mr. Elonis’s trial, his estranged wife testified that she understood the posts as threats.

“I felt like I was being stalked,” she said. “I felt extremely afraid for mine and my children’s and my family’s lives.”

Mr. Elonis was convicted under a federal law that makes it a crime to communicate “any threat to injure the person of another.” He was sentenced to 44 months.

John P. Elwood, a lawyer for Mr. Elonis, said his client’s posts included elements of entertainment. Justice Samuel A. Alito Jr. responded warily.

“This sounds like a road map for threatening a spouse and getting away with it,” Justice Alito said. “You put it in rhyme and you put some stuff about the Internet on it and you say, ‘I’m an aspiring rap artist.’ And so then you are free from prosecution.”

The Supreme Court has said that “true threats” are not protected by the First Amendment, but it has not been especially clear about what counts as such a threat. Justice Anthony M. Kennedy said the term itself was unhelpful.

“I’m not sure that the court did either the law or the English language much of a good service when it said ‘true threat,’ ” he said. “It could mean so many things.”

The question for the justices in Monday’s case, Elonis v. United States, No. 13-983, was whether prosecutors had done enough to prove Mr. Elonis’s intent. Mr. Dreeben, the government lawyer, said the words and their context were enough.

The standard proposed by the government, he said, would hold people accountable “for the ordinary and natural meaning of the words that they say in context.”

Mr. Elwood said more was required. Ideally, he said, prosecutors should have to prove that the speaker’s purpose was to threaten someone. Failing that, he said, prosecutors should at least have to prove that the speaker, whatever his or her purpose, knew “that it’s a virtual certainty” that someone would feel threatened.

The lower courts sided with Mr. Dreeben, the government lawyer. All the prosecution had to prove, the trial judge ruled, was that a “reasonable person” would foresee that others would view statements “as a serious expression of an intention to inflict bodily injury or take the life of an individual.”

“This is distinguished,” the judge said, “from idle or careless talk, exaggeration, something said in a joking manner or an outburst of transitory anger.”

Monday’s argument was mostly about calibrating and articulating the right level of intent, and it seemed that many of the justices were looking for something between mere negligence and purposeful conduct. There was perhaps the beginning of a consensus that it would be enough to require prosecutors to prove that Mr. Elonis had been subjectively aware that his posts would scare and disturb his wife.

The court could ground such a ruling in the First Amendment or in interpreting the federal law on threats, though the latter seemed more likely.

But some justices seemed nervous about placing too stringent a burden on prosecutors.

“How does one prove what’s in somebody else’s mind?” Justice Ruth Bader Ginsburg asked. “In this case, the standard was ‘Would a reasonable person think that the words would put someone in fear?’ and reasonable people can make that judgment. But how would the government prove whether this threat in the mind of the threatener was genuine?”

That echoed Mr. Dreeben, who insisted that the proper standard was an objective one that looked to what a reasonable person would have understood in the circumstances.

Chief Justice Roberts tried to refine the point.

“Is it a reasonable person?” he asked. “Or is it a reasonable teenager on the Internet?”

There was laughter, and then Mr. Dreeben responded. “If there is such a thing,” he said.