Hosni Mubarak waved to his supporters from inside a defendant's cage on Saturday after being wheeled into a Cairo courtroom for the first session of his retrial on charges of complicity in the killing of demonstrators during the 2011 revolt that led to his ouster.

The procedural session ended quickly when the judge recused himself, referring the case to an appeals court for a replacement.

Mubarak grinned slightly as he sat upright on a hospital gurney inside the defendants' cage made of iron bars and wire mesh. His once powerful two sons, Alaa and Gamal, and former interior minister, Habib el-Adly, who are currently imprisoned in separate cases, were in the cage alongside him.

Mubarak is the first Arab president to be tried and serve a prison sentence. He remains in custody at a military hospital and is additionally being investigated on accusations that he and his family pocketed state funds designated for presidential palaces.

The 84-year-old ousted Egyptian leader, wearing brown-tinted glasses, had not been seen in public since his initial conviction in June 2012. Unconfirmed reports surfaced several times in the past year suggesting that he was near death.

He was airlifted by a military helicopter to the court located inside a police academy once named after him. His two sons and el-Adly were driven from Tora prison.

Judge Mostafa Hassan recused himself from the trial, but did not specify the conflict of interest behind the decision.

As he took the bench, some lawyers shouted, demanding that he step down from the case.

"Sit until you hear what the court's decision is," the judge responded.

Immediately after he announced that the case would be sent to an appeals court, some lawyers began chanting, "The people demand the execution of the ousted president!"

Local media reports had suggested Hassan might transfer the case to another judge. In October, he caused an uproar among Egyptian political activists when he ordered the acquittals of 25 Mubarak loyalists who had been accused of organizing a deadly attack during the 18-day revolt in which assailants on horses and camels stormed downtown Cairo's Tahrir Square.

Mubarak and el-Adly's retrial was granted by an appeals court that overturned their life sentences in January. The presiding judge of that first trial said the prosecution's case lacked concrete evidence and failed to prove the protesters were killed by the police during the bloodiest days of the uprising between Jan. 25-30.

If convicted again, the life sentences handed to Mubarak and el-Adly would be upheld. They also could have their sentences reduced or even be acquitted. It is considered unlikely that they would draw a heavier sentence, like the death penalty.

In addition to Mubarak's charges related to the deaths of protesters, he and his sons face corruption charges in the trial along with longtime business associate, Hussein Salem, who is currently on the run in Spain. Five police generals face the same charges as Mubarak with relation to the killing of protesters while a sixth is accused of gross negligence.

Mubarak's two sons and the six police generals are being retried after prosecutors filed an appeal against their acquittals.

The ruling in Mubarak's first trial prompted mass protests against the mixed verdict, which sentenced the former president to life in prison but failed to bring about full accountability for wrongdoing under his rule.

Hoda Nasrallah, a rights lawyer representing 65 victims' families in the case, said there is no certainty that the prosecution will provide new evidence this time around that could back up the charges.

The judge in the first trial had criticized the prosecution for failing to provide evidence that police killed protesters. Protesters accused the office of the attorney general, who was a Mubarak-appointee at the time, of doing a shoddy job at collecting evidence.

"The investigations took place in just one month, which is not enough time to review all the cases of killings across Egypt," Nasrallah said. "There are reports in the media that there will be new evidence submitted, but we're waiting to see if that is true."

The scene outside of the courthouse highlighted the stark difference in Egypt's political atmosphere compared to the emotions evoked during Mubarak's first trial in August 2011.

Hundreds flocked to the courtroom for his first trial and Egyptians and others in the region were glued to televisions in near-disbelief at seeing the former autocrat in a courtroom cage _ a symbol to many of the people's triumph over dictatorship.

The retrial drew only a few dozen Mubarak opponents and supporters, who briefly threw stones at each other before police intervened.

More than two years after his ouster, Egyptians are reeling from a myriad of problems that include fuel shortages, growing unemployment and political polarization that has at times led to deadly street battles between different factions.

In earlier court appearances, Mubarak's two sons would often stand to shield their father from the cameras, but at the start of the new trial Mubarak appeared to be grinning at times as he waved to his supporters. His wave seemed to suggest a nod to increasing nostalgia among some Egyptians for his rule, when tourism and other vital economic pillars fared better.

The former president, who ruled Egypt for 29 years, has remained in custody since his conviction, spending some time in a prison hospital before being transferred to a military one on grounds that he needed better medical care. Prosecutors are requesting he be transferred back.

A high-level inquiry into the deaths of the nearly 900 protesters killed in the uprising, parts of which were released exclusively to The Associated Press last month, could weigh heavily in the retrial. It found that police were behind nearly all the killings, using snipers on rooftops overlooking Tahrir Square to shoot into huge crowds.

The inquiry determined that such deadly force could only have been authorized by el-Adly with the ousted president's full knowledge.

The judge has the discretion to decide whether to accept the new fact-finding committee's report, which must first be sent to the prosecutor's office. The prosecution is tasked with further investigating its findings, and then decides if it wants to include the report in its case file to the court. Meanwhile, the judge can exclude parts of the report that might implicate people not included in the case since the court cannot press charges.

The fact-finding commission was created by Mubarak's successor Mohammed Morsi after his election win last summer and campaign promises of bringing former officials to justice.

Morsi's Muslim Brotherhood supporters, though, have spoken out in support of so-called reconciliation talks with former officials, many of whom have been acquitted and released from prison in recent months.

Additionally, nearly 100 police officers have faced trial over the killing of protests during the revolt. All except two were acquitted.