US actor Jussie Smollett's conviction on charges he staged a racist and homophobic attack against himself and lied to police has been overturned over prosecutorial issue.
The Illinois Supreme Court decision on Thursday did not address his claim of innocence.
The state's highest court found that a special prosecutor should not have been allowed to intervene after the Cook County state's attorney initially dropped charges against Smollett in exchange for him forfeiting his $US10,000 ($A15,000) bond and conducting community service.
Jussie Smollett took to the stand in his own defence at his trial in Chicago in 2021. (AP PHOTO)
Smollett, who is Black and gay, claimed two men assaulted him in downtown Chicago in 2019, spouted racial and homophobic slurs and tossed a noose around his neck, leading to a massive search for suspects by Chicago police detectives and kicking up an international uproar.
Smollett was on the television drama Empire, which filmed in Chicago, and prosecutors alleged he staged the attack because he was unhappy with the studio's response to hate mail he received.
"We are aware that this case has generated significant public interest and that many people were dissatisfied with the resolution of the original case and believed it to be unjust," Justice Elizabeth Rochford wrote in the court's 5-0 opinion.
"Nevertheless, what would be more unjust than the resolution of any one criminal case would be a holding from this court that the state was not bound to honour agreements upon which people have detrimentally relied."
Smollett's Lawyers argued the case was over when Cook County State's Attorney Kim Foxx's office dropped an initial 16 counts of disorderly conduct. The deal prompted immediate backlash, with then-Mayor Rahm Emanuel calling it "a whitewash of justice". A special prosecutor was appointed, and a grand jury restored charges, leading to Smollett's 2021 conviction on five counts of disorderly conduct.
"This was not a prosecution based on facts, rather it was a vindictive persecution and such a proceeding has no place in our criminal justice system," Smollett's lawyer, Nenye Uche, said in a statement.
Uche said "rule of law was the big winner today" and thanked the court for "restoring order to Illinois' criminal law jurisprudence".
Special prosecutor Dan Webb said he disagreed with the court's ruling while noting it "has nothing to do with Mr. Smollett's innocence".
"The Illinois Supreme Court did not find any error with the overwhelming evidence presented at trial that Mr. Smollett orchestrated a fake hate crime and reported it to the Chicago Police Department as a real hate crime, or the jury's unanimous verdict that Mr. Smollett was guilty of five counts of felony disorderly conduct," Webb said.
A spokesperson said Foxx would be available to comment later on Thursday. Eileen O'Neill Burke, the incoming Cook County state's attorney who was elected this month to replace Foxx after she decided not to seek a third term, declined to comment.
Testimony at trial indicated Smollett paid $US3500 ($A5300) to two men whom he knew from Empire to carry out the attack. Prosecutors said he told them what slurs to shout, and to yell that Smollett was in "MAGA country," an apparent reference to the Donald Trump's presidential campaign slogan.
Smollett testified that "there was no hoax" and that he was the victim of a hate crime in his downtown Chicago neighbourhood.
He was sentenced to 150 days in jail - six of which he served before he was freed pending appeal - and was ordered to pay about $US130,000 ($A199,000) in restitution.
Webb noted that Chicago officials can still pursue their civil case against Smollett that seeks to recoup the $130,000, the amount police say they paid in overtime to pursue Smollett's accusations.
Illinois Supreme Court Chief Justice Mary Jane Theis and Justice Joy Cunningham took no part in Thursday's decision.