CAIRO -- Hosni Mubarak, 83 years old and ailing, goes on trial today on charges of corruption and ordering the killing of protesters during the 18-day uprising that toppled him, and many Egyptians are celebrating the chance at retribution against a longtime authoritarian ruler.

But they also question whether the trial will truly break with the injustices of the past. Some worry that Egypt's new military rulers are touting the trial as proof that democratic reform has been accomplished, even as activists argue that far deeper change is still needed.

"I am a little worried that if Mubarak is tried and convicted people will take that to be the end of the revolution. They will say that the revolution has realized its goals. This should not be the case," said Tareq Shalaby, a social media consultant who was among the hundreds of thousands of protesters who thronged Cairo's Tahrir Square and other cities during the uprising.

The prosecution of the ousted president is an unprecedented moment in the Arab world, the first time a modern Mideast leader has been put on trial fully by his own people.

The closest event to it was former Iraqi leader Saddam Hussein's trial, but his capture came at the hands of U.S. troops in 2003 and his special tribunal was set up with extensive consultation with American officials and international experts. Tunisia's deposed president, Zine El Abidine Ben Ali, has been tried and convicted several times since his fall several weeks before Mubarak's, but all in absentia and he remains in exile in Saudi Arabia.

Mubarak, who ruled with unquestioned power for 29 years, is expected to appear during the trial sitting in a cage set up for him and his co-defendants, including his two sons and his former interior minister. The charges could bring a death sentence, traditionally carried out by hanging.

In an ironic twist, the courtroom has been set up in what was once the Mubarak Police Academy -- one of the multiple security, military and other civil buildings named after the president, though since his Feb. 11 ouster his name has been dropped. Security will be tight, with barbed wire and hundreds of troops around the compound. Efforts have been made to ensure spectators in the court can't get close enough to the defendants' case to yell and throw objects at them, the Interior Ministry said.

Mubarak's trial came only after heavy pressure by protesters. For weeks after his fall, as Mubarak lived in a palace in the Red Sea resort of Sharm el-Sheikh, the ruling generals, who were all appointed by Mubarak, appeared reluctant to prosecute him. A trial was one of the few demands that still united the disparate protest movement.

Their hand forced, the generals now seem eager to show the public that they are bringing the fruits of the revolution. The trial will be televised live on state TV, and judges say proceedings will be expedited, without long postponements. The around 600 people attending are expected to include relatives of some of the 850 protesters killed during the uprising.

"The Pharaoh in the defendants cage!" gloated a banner headline Tuesday in the independent El-Osboa newspaper alongside a photo-illustration of Mubarak behind bars.

The night before proceedings were to begin, Mubarak was still at the Sharm hospital. Security officials said he would be flown by helicopter directly to the police academy just before the session.

That only fueled worries that Mubarak would not attend for health reasons, after weeks of reports of his worsening condition from the Sharm hospital where he has been held in custody. If he does not attend, it is likely to cause an uproar.

"The streets will not be quiet if this happens," said Nadim Mansour, a rights activist.

For the military, the trial is a chance to try to strengthen its position.

The broader public has grown discontented with the breakdown in security around the country and faltering economy since the uprising began.

Youth groups that led the uprising have continued protests against the military, saying they are fumbling the transition to civilian rule and have not moved to dismantle remnants of Mubarak's regime still in place. The military itself has been tainted by reports of human rights violations, including torture.

The generals have tried to turn the public against activists, accusing them of receiving foreign funds and training. On Monday, tensions were hiked when troops broke up a 3-week-old sit-in in Tahrir Square by hard-core protesters.

Prosecuting Mubarak is widely popular among a public angered by widespread corruption, police abuses and his lock on political power. Regime opponents, whether Islamists or pro-democracy activists, are eager for retribution after years of crackdowns and torture against them.

The question is whether it will mean a real uprooting of the system he headed.

"The trial can signal a break with the past but only if people can see that the proceedings are clean and transparent. But what happened in Mubarak's 29 years will not be erased in a day or two or a week," said Shady Dawoud, a 24-year-old university graduate who is among the ranks of Egypt's unemployed. "It does not amount to the end of his regime, that will take 10 years or so."

Negad Borai, a lawyer and human rights activist, said the trial "will seal the past and inspire people to turn the page and start working for the future."

Mubarak, his former Interior Minister Habib el-Adly, and six top police officers are charged with murder and attempted murder in connection with the 850 protesters killed during the uprising, according to the official charge sheet. All eight could face the death penalty if convicted.

Separately, Mubarak and his two sons -- one-time heir apparent Gamal and wealthy businessman Alaa -- face charges of corruption.

Mubarak was placed under arrest in April but was admitted to the Sharm hospital for a heart condition, sparing him the indignity of detention in Cairo's Torah Prison, where his sons and some three dozen former regime figures have been held.

Media reports have spoken of Mubarak refusing to eat and suffering from depression. On Monday, state television said the most recent tests showed his health was "relatively stable" given his age but that his psychological condition was worsening.

But Health Minister Amr Helmy said last week that Mubarak was fit to travel to Cairo to stand trial.