If convicted in the trial, which began on Tuesday, the police officers could face between three and 15 years in prison.

Al Jazeera's Ayman Mohyeldin reporting from the Alexandria courthouse, 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 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."

Mohyeldin said: "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."

Autopsy questioned

An official autopsy is said to have concluded that Said 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."

Witnesses say two plainclothes policemen dragged Said away from an internet cafe in Alexandria on June 6 after he refused to show them his identification.

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

'Culture of injustice'

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.