A garda who used pepper spray and pinned down a homeless man with his foot did not use excessive force during his arrest, an inquiry found.
The Garda watchdog cleared the officer of any wrongdoing during the arrest of the 34-year-old on Dublin's Henry Street on March 13.
A special investigation in the public interest was launched by the Garda Síochána Ombudsman Commission (GSOC) after partial footage of the incident - posted on the internet by a student - went viral and 17 people complained.
The garda involved in the incident said he used incapacitant spray twice because he feared he would be assaulted by the man, who was 6ft 5in tall.
He denied using excessive force or that he used the spray after the man was restrained by handcuffs.
It found the garda's account was supported by CCTV footage, which showed the drunken homeless man trying to punch him and grab his pepper spray.
Attempts to enhance the uploaded footage captured on a camera phone also proved "inconclusive as to whether incapacitant spray had indeed been used by the garda when the man was handcuffed on the ground".
"Insufficient evidence of either a criminal or disciplinary nature was established in the investigation," GSOC said.
"It appears that any force used by the garda concerned in this incident was justified, lawful and proportionate under the circumstances and no more than absolutely necessary."
GSOC said the man was initially found slouched against the shutters of a shop on Henry Street, near the GPO, at 3.20pm and told to move.
Ten minutes later he was seen under a sleeping bag by the same garda outside an empty shop on Henry Street, where the officer was verbally abused.
As he tried to arrest him, the man drew his hand up across his chest.
The garda said when he first deployed his incapacitant spray it had minimal effect and the man tried to kick out and punch at him.
"He sprayed the man for a second time and called for assistance using his radio," it added.
The man, interviewed through a Polish interpreter, had no memory of the incident and did not personally lodge any complaint against gardaí.