The Arkansas case now returns to the lower court for further proceedings. (Representational)

The mere act of yelling an expletive at a police officer is constitutionally protected speech and not grounds for arrest, a federal appeals court ruled Monday.

The decision by a panel of the US Court of Appeals for the 8th Circuit followed a ruling in March by the US Court of Appeals for the 6th Circuit that stopping and ticketing a woman for giving an officer the finger violated her constitutional rights.

Monday's case began when a 20-year-old man, Eric Roshaun Thurairajah, yelled "f--- you" out of his car window at an Arkansas state trooper, Lagarian Cross, from the other side of a five lane Fort Smith highway where Cross had made a traffic stop.

In a deposition, Thurairajah had no explanation for his abusive comment. He was not acquainted with Cross or the woman who had been stopped by the officer across the highway.

"I mean, as far as, like, state troopers go, I mean, I don't think anybody likes them," he said in his deposition. "I mean, like they say, even, like, the city police don't like state troopers. So it's like, I don't know."

According to the ruling, Cross ended his traffic stop and took off after Thurairajah, ultimately arresting him for disorderly conduct, specifically for making "unreasonable or excessive noise."

Thurairajah was jailed for several hours before charges were dropped, according to the opinion. He then sued the officer for violating his civil rights - under the Fourth Amendment's guarantee against unreasonable seizures and for allegedly retaliating against him for exercising his First Amendment rights.

The officer, represented by the state of Arkansas, claimed qualified immunity from the suit. But both the district court that heard the case originally and now the appeals court that upheld it said officers are not immune when they violate the Constitution.

In this case, that's just what Cross did, the appeals court in St. Louis said.

"Thurairajah's profane shout was protected activity," Smith wrote, citing years of precedent. "Criticism of law enforcement officers, even with profanity, is protected speech."

"Thurairajah's shout," he said, "was unamplified and fleeting, no crowd gathered because of it, city traffic was not affected, no complaints were lodged by anyone in the community, a business was not interrupted, nor were an officer's orders disobeyed."

But "in no case, has a two-word unamplified outburst constituted disorderly conduct."

The March "flipping the bird" case, as a judge called it, involved a Michigan woman who gave an officer the finger as he drove away after ticketing her. The gesture prompted him to stop and ticket her again. She sued and won. That "all-too-familiar gesture," appeals court Judge Jeffrey Sutton wrote, is "protected by the First Amendment."

The Arkansas case now returns to the lower court for further proceedings, barring an appeal.

"The attorney general is disappointed in the 8th Circuit Court's decision and is reviewing the case to determine the next steps," said Amanda Priest, a spokeswoman for Arkansas Attorney General Leslie Rutledge.

Whitfield Hyman, the lawyer representing Thurairajah, said his client "has grown up a lot" since the 2015 incident.