WASHINGTON--The U.S. Supreme Court on Wednesday grappled with a convicted stalker's claim that thousands of unwanted Facebook messages he sent to a female musician in Colorado were protected speech in a case testing the limits of the U.S. Constitution's First Amendment safeguards. In arguments in the case, the justices explored the question of when offending statements rise to the level of a true threat, which the Supreme Court has long viewed as a type of speech that falls outside of constitutionally protected free speech guardrails. Billy Counterman, found guilty in a 2017 trial and sentenced to 4-1/2 years in prison, is challenging his conviction under a Colorado stalking law after a state court ruled that his messages to Denver singer-songwriter Coles Whalen were a threat and thus not constitutionally shielded. Counterman has a history of making violent threats to women and was on supervised release from one such federal conviction during the two years he continuously messaged Whalen. The stalking law at issue does not require proof of a speaker's subjective intent to intimidate. Rather, Counterman was convicted based on a showing that his messages would cause a "reasonable person" serious distress, a so-called objective legal standard. Some justices questioned whether using a reasonable person standard to assess purported threats might lead to improper convictions. "We live in a world in which people are sensitive, and maybe increasingly sensitive," conservative Justice Neil Gorsuch told Colorado's attorney general. "Reasonable people may deem things harmful, hurtful, threatening, and we're going to hold people liable willy-nilly for that?" Counterman contends that prosecutors should be required to prove a speaker's specific intent to threaten before stripping offending speech of its legally protected status. Conservative Justice Clarence Thomas noted that a speaker's intent need not be proven in cases involving obscenity, another type of speech that falls outside First Amendment protection. "Why should these true threats receive more protection than obscenity?" Thomas asked Counterman's lawyer John Elwood. Whalen has described the messages from Counterman, which came to her over a two-year span beginning in 2014, as life-threatening and life-altering. Whalen has said Counterman sent thousands of messages to her personal and public Facebook accounts, some of which suggested he had seen her in public. She never responded to Counterman during this time and blocked his Facebook account at least four times, prompting him to continue messaging her from other platforms or through new Facebook accounts he created. Among Counterman's communications to Whalen were messages that read: "Was that you in the white Jeep?" and "You're not being good for human relations. Die. Don't need you." Others used expletives. Whalen said the messages eventually left her paralyzed with fear and anxiety, causing her to cancel shows and turn down career opportunities, and leading her to apply for a concealed handgun permit and sleep with a light on. Whalen in 2016 discussed her concern about the messages with a family member, who alerted law enforcement. Colorado prosecutors later that year charged Counterman with stalking, which state law defines in part as communication that "would cause a reasonable person to suffer serious emotional distress." Counterman, citing mental illness and delusions, argued his statements were never intended to be threatening and were thus protected speech. The First Amendment prohibits the government from enacting laws "abridging the freedom of speech," but the U.S. Supreme Court has decided that the provision does not protect true threats. A trial court denied Counterman's First Amendment defense and a jury convicted him. His appeal was rejected by the Colorado Court of Appeals. Colorado's top court declined to review the case.