Egypt's court of cassation has refused an appeal by prosecutors over the "Camel Battle" trial.
Judge Hamed Abdullah's decision Wednesday against the prosecution's appeal raises calls for new investigations into the February 2, 2011 assault, in which supporters of Hosni Mubarak, then Egyptian president, charged into a sit-in in Cairo's Tahrir Square on camels and horses, setting off clashes that lasted into the next day and left nearly a dozen dead.
"The court has made this final decision on the fate of the 24 defendants who were accused of conspiring to kill protesters in that infamous incident," said Al Jazeera's Rawyeh Rageh, reporting from Cairo.
Judges argued witnesses were unreliable and evidence against the defendants, some of the biggest names in the Mubarak government, was weak.
"These defendants were acquitted last year, sending shockwaves into the Egyptian community," our correspondent said.
In October, a court acquitted the 24 Mubarak loyalists. The defendents were found innocent on charges of manslaughter and attempted murder.
The mounted attack, which included whip-wielding riders, became a symbol of the revolution and led to street clashes.
The scenes were televised around the world at the height of the uprising.
Families of the victims reacted angrily at the appeals court decision, which is final and cannot be retried.
"How is it that all of these officials are being acquitted after the revolution," Hamdeya Gaber, mother of slain victim Nasr Eldin Eweis, told Al Jazeera's Rawya Rageh.
"No one can convince me these people are innocent. We all saw what happened in Tahrir, the whole world saw," Gaber said. "If this absence of justice continues, there will be another revolution".
On February 1, a day before the attacks, Mubarak made his second speech to address the nation amid massive protests.
"The thing that pains our hearts the most is the fear that has taken over the sweeping majority of Egyptians …. the events force us to choose between chaos and stability," he said.
At least 11 people were killed in the "battle", and as many as 1,000 injured.
In July 2011, investigators found that a former speaker of Egypt's upper house of parliament was behind the attacks.
The fact-finding judicial committee ruled that Safwat al-Sharif masterminded the February 2 assault that left several protesters dead.
The investigation concluded that Sharif and other parliamentarians had hired thugs to attack crowds and that he urged them to "kill the protesters if they had to", the state-run MENA news agency reported.
The trial began in September 2011; Sharif, Fathi Sorour, former speaker of the lower house and the rest of those appearing in court denied the charges filed against them.
In October 2011, an Egyptian court acquitted the defendents because the testimony of the witnesses was weak and "driven by grudges between witnesses and the defendants due to partisan differences," according to Judge Mustafa Abdullah.
He also said some of the witnesses had criminal records, including one who had a record of perjury.
Despite the list of known victims, the judge said he trusted the testimony of a general who was a member of the council
that ruled Egypt during the transition, who said that no one was killed in the square during the battle.