The snap rally on October 9 was sparked by a decision to light the Opera House's sails in the colours of the Israeli flag after the Hamas attack that sparked the latest Israel-Gaza conflict.
Several protesters at the rally held signs criticising Israel and its government, including descriptions of the nation as a terrorist state.
Edited footage of protesters chanting and a caption reading "gas the Jews" was later shared by the Australian Jewish Association with news organisations and on social media, leading to widespread condemnation and changes to hate-crime laws.
But NSW Police, which had come under fire for not intervening at the event, said an independent expert found no evidence the chant occurred, after combing over numerous audio and video files from the rally.
"(The expert) has concluded with overwhelming certainty that the words used were 'where's the Jews?," Deputy Commissioner Mal Lanyon said on Friday.
Mal Lanyon says forensic experts found no evidence the chant was used. (Bianca De Marchi/AAP PHOTOS)
While several witnesses had signed statutory declarations that they heard the "gas" phrase, Mr Lanyon said detectives relied on the evidence of the "eminent and very experienced" expert.
He accepted other offensive words were used but underlined the importance of accurate information being presented in the public arena.
"We would hope as a police force that this will ensure that community safety and balance remains," he said.
Detectives continue to ask anyone with information who may not have yet spoken with police to come forward.
But federal Opposition Leader Peter Dutton dismissed the police decision while highlighting that the Jewish community remained in fear in the face of rising anti-Semitism.
"The accounts from that night speak for itself - it was a moment of national shame," he said.
Jewish leader Alex Ryvchin also backed those who provided statements to police, saying "the world knows what was said".
But the exact words used were not the core issue, he added, noting that the Opera House rally came before Israel started its military response to the Hamas attack, which was the deadliest day for Jewish people since the Holocaust.
"A mob of thugs gathered at one of our nation's most cherished sites to celebrate the mass slaughter and rape of Israelis, to burn Israeli flags and to chant threateningly towards fellow Australians," the Executive Council of Australian Jewry co-chief executive said.
Many pro-Palestinian activists and Arab elders expressed disgust at some actions at the rally. (Dean Lewins/AAP PHOTOS)
Australian Jewish Association president David Adler told AAP he was unable to immediately comment as he had not seen the police statement.
At the time of the protest, Premier Chris Minns led a host of prominent figures condemning the rally and the "shocking and abusive" comments reportedly made there.
NSW Opposition Leader Mark Speakman also criticised police for approving the march and warning the Jewish community to steer clear of the Opera House forecourt.
"This was meant to be a chance for our Jewish community to have a peaceful vigil ... and instead it's allowed to be hijacked by a rowdy mob shouting anti-Semitic slogans, lighting flares and burning a flag," he said.
The "gas" chant was cited numerous times in a debate over hate crime laws including when MPs streamlined procedure for police to begin prosecutions in late November.
Protest organisers Palestine Action Group previously rejected claims "gas the Jews" was uttered at the protest, while attributing a similar comment - "f*** the Jews" - to a tiny fringe of "vile anti-Semitic attendees".
The ugly scenes were preceded by dozens of peaceful pro-Palestine demonstrations across the nation, including several attended by thousands of people in Melbourne and Sydney.
