If convicted, the two officers could face between three and 15 years in prison.

'Significant case'

The case has sparked widespread public protests in the country, where security forces have enjoyed broad powers and acted with impunity under Hosni Mubarak, the president.

"For far too long, some police officers and security officials in Egypt have acted as if they believe themselves to be above the law"

Malcolm Smart,
Amnesty International

Prosecution of police officers is rare in the country, but many government critics and human rights activists say this case could prove a turning point and end what they describe as a deeply rooted culture of official brutality.

Al Jazeera's Ayman Mohyeldin, reporting from Alexandria, said: "Standing outside the courthouse, you really get a sense of how significant this case has become in a country that has been ruled by emergency law for nearly 30 years.

"It has been used by politicians to make the case that issues of torture and abuse are rampant by Egyptian police and security services. 

"Egypt's security apparatus is a very complex layer of several forces that answer to the ministry of interior and internal intelligence so the concern among many people is that these security services really go unchecked."

"There is a lack of a transparent judicial process and people fear that when cases like these happen and they do not surface, many of them go unpunished."

Hundreds of riot policemen cordoned off the court in the city of Alexandria as the trial started. Dozens of human rights activists protested outside, waving pictures of Said.

Autopsies questioned

Two official autopsies ordered by Egypt's state prosecutor concluded that Said had died of asphyxiation as a result of swallowing a plastic roll full of drugs and that the injuries sustained during his arrest did not cause his death.

However, these findings have been widely questioned amid accusations that they are part of an attempted cover-up by the ministry of interior.

Egypt's Nadeem Centre for the Rehabilitation of Victims of Violence has called for a new autopsy to be conducted by an independent pathologist.

"The forensics report never explained why there was blood coming out of the boy’s ears and nose, which usually results from a fractured skull," Magda Adly, the director of the Nadeem Centre, told Al Jazeera.

"It made other astonishing claims in line with the government's account that have long been considered a joke, such as young men dying in custody suddenly because of diarrhoea, asthma, or a cellmate crushing them in their sleep."

Graphic pictures of a bruised and battered Said have appeared on social networking websites, triggering much of the outcry.

Witness protection

Witnesses said that they dared not interfere as they watched the officers repeatedly slam Said's head into stone steps until he was dead.

Malcolm Smart, the director of Amnesty's International's Middle East and North Africa Programme, called on the Egyptian government to make sure that justice is done and witnesses are protected.

"For far too long, some police officers and security officials in Egypt have acted as if they believe themselves to be above the law, which has bred a culture of injustice and impunity," he said in a statement on Monday.

"It is high time that this was brought to an end, once and for all.

"The Egyptian authorities must ensure that the witnesses to the assault on Khaled Mohammed Said are provided with all possible protection both to ensure their own safety and as a means of encouraging other witnesses to come forward."

Some senior Egyptian officials including Gamal Mubarak, the president's son, have already spoken out against the officers actions.