Preliminary investigations magistrate Maurizio De Matteis said there was enough evidence to indict 45 state officials on charges of abuse, fraud, criminal coercion and inhuman and degrading treatment.
Over 250 activists, including several British nationals, have complained of their treatment after being arrested and taken to a holding centre outside Genoa during the July 2001 summit.
They say they were spat at, verbally and physically humiliated, and threatened with anal and vaginal rape.
Prosecutors also reported that one woman had her head thrust down a toilet, while a man was ordered to crawl around on his hands and knees and bark like a dog.
Five medical workers, including the garrison's most senior doctor, Giacomo Toccafondi, are charged with insulting detainees during their examinations and failing to inform authorities after asphyxiating gas was sprayed into protestors' cells.
A pressure group set up in the wake of the summit, the Committee for Truth and Justice, hailed the decision as "positive" but warned that the proceedings still faced a major hurdle.
"Unfortunately, the delays in bringing these people to trial means that the statute of limitations will probably have expired on the worst charges," the committee's president, Enrica Bartesaghi, whose daughter was among the detainees.
"By the time the trial starts on October 12, the abuse charges will almost have hit their five-year deadline. This means prosecutors will only be able to request convictions on the more minor charges, such as fraud and failing to allow non-Italians access to their consulates."
A lawyer for 11 of the indicted Carabineri officers, Alfredo Biondi, expressed his concern, implying that junior officials were taking the rap for decisions made higher up the chain.
"I'm not surprised but I am bitter," said Biondi, who is an MP with Premier Silvio Berlusconi's centre-right Forza Italia party and Deputy Speaker of the lower parliamentary chamber.
"They had no choice in being posted to the garrison and were just trying to do their duty.
"These men were all junior officers and are being charged for failing to act, while Alfonso Sabella, who was overseeing the entire operation, has emerged from the affair unscathed."
Sabella, a high-profile state prosecutor, was the penitentiary police's chief investigator at the time.
The hearing regarding abuse at the garrison in Bolzaneto is one of three separate judicial investigations into events at the violence-marred summit.
Twenty-five demonstrators are being tried on charges of looting and ransacking during clashes with police.
Meanwhile, a trial is set to resume on Thursday against 28 senior police officers regarding alleged brutality during a raid on a school that was housing many of the protestors at the time.
More than 60 demonstrators were injured during the raid, three of whom were placed on a critical list, after police in riot gear burst into the Diaz school in the early hours of July 22.
The police say the protesters were harbouring dangerous weapons and that they resisted arrest, responding with violence.
However, Genoa prosecutors have since dropped all charges against the 93 demonstrators arrested during the raid.
The police, meanwhile, stand accused of planting evidence, including two Molotov cocktails, and falsely accusing the protesters of attacking them and resisting arrest.
Some 200,000 demonstrators converged on Genoa for the G8 summit.
During two days of mayhem, a 23-year-old protestor, Carlo Giuliani, was shot dead by a policeman, shops and businesses were ransacked and hundreds of people injured in clashes between police and demonstrators.