The last time Gamal Siam saw his son in a crowded prison cell in Cairo, Sherif asked him to bring some ice-cream, so he could share it with the other inmates. "He loved ice-cream," Siam said softly. Little did he know, that the next time he would see his youngest son - a handsome 28-year old communications engineer with a round, happy face smiling broadly in the many pictures his family has propped up on tables and sideboards in their flat in an affluent neighborhood in Cairo - would be at his funeral.

Early the next day, on the 18th August 2013, Sherif and 44 other men were bundled into a small prison van, which had the capacity to hold half as many prisoners. The men had been arrested during the mass protests following the toppling of a former president and member of the Muslim Brotherhood, Mohamed Morsi by the army. This followed weeks of mass protests against his rule, which many saw as increasingly undemocratic and authoritarian. Six weeks later, on the 14th August, security forces moved into the camp at Rabaa, killing and arresting hundreds of protesters in the course of several hours.

'I should have made him stay at home'

Sherif, his father, an emeritus professor of agricultural economics at Cairo University, told DW, was not a member of the Muslim Brotherhood, not even a sympathizer. He had gone to the protest camp on the morning of the violent crackdown to help with the injured. "I feel tormented," his father said, "I should have stopped him from going to the sit-in, I should have made him stay at home, it was such a dangerous day."

Six days later, as the van holding Sherif and the other men, all of them accused of assault, possession of weapons and an array of other charges their families emphatically reject, slowly made its way to Abu Zaabal, a military prison north-east of Cairo, the temperatures began to rise. "We were suffocating in the van, it was so hot,” one of the only eight survivors told DW. It was so crowded in the van, according to 61-year old Hussein Abdel Aal "that we could barely move, some people were lying on the floor piled on top of each other. They transported us like sheep."

Prisoners were kept locked inside the van for hours

Abdel Aal said he had made his way to Rabaa on the day of the crackdown to beg his son, a medical doctor and member of the Muslim Brotherhood who was working at the make-shift hospital, to leave the protest and come home with him. A few hours later, he told DW, his son, a father of two, was shot in the head and Abdel Aal was dragged from the ambulance transporting his injured son, who died a few hours later in hospital.

On a Sunday morning, it took an hour for the prison van transporting Sharif, Abdu Aal and the other men to arrive at Abu Zaabal. For hours, the prisoners were kept locked inside the van in the prison courtyard, and soon people began collapsing. "We banged on the door and begged the police officers for help," Hussein Abdel Aal, who says he survived because he was standing close to the door, told DW on a phone line from his hometown Mansoura. The officers ignored their pleas, he said, jeering and laughing at the men suffocating inside. Only once, Abdel Aal said, did officers throw some water through the tiny, barred windows. "Only some of us were able to catch some in our hands."

Some eight or nine hours later, around 2 p.m. when police officers finally opened the door, according to the two survivors, most men were barely conscious. As Abdel Aal staggered out of the door, he recalled, police officers started firing tear gas into the van.

'People were lying on the floor, barely moving'

According to another survivor DW interviewed, Mohamed Abdelmahboud, the tear gas was thrown into the van shortly before the doors were opened. “My eyes burnt and I couldn't breathe, it suffocated us," Abdelmahboud recalled. Abdel Aal concedes that it is possible that the gas was fired while he was still in the van: "I was only half-conscious, who knows." He told DW that when he was outside, a police officer smeared some “phosphorous substance on my face.”

Did the tear gas kill those inside the van? Survivor Abdu Aal can't say for sure: "I'm not a doctor. Many people were already lying on the floor, barely moving." As he left, he said, he nudged one man lying on the floor. "He didn't even move, maybe he was dead, I don't know." Abdelmahboud agrees: "How can I say if it killed them? People had fainted. Maybe they were already dead."

It's possible that the tear gas killed some of the men, but it's also likely that at least some of them were already dead at that point. But why did the police officers fire the tear gas into the crowded van full of semi-conscious prisoners? The official account is that prisoners tried to kidnap a police officer, forcing the guards to fire tear gas in an act of self-defense to free him. It's a lie, survivors say. "Look, it doesn't make any sense," Abdelmahboud told DW, "we could barely move, let alone hold a police officer hostage."

This is not a fair trial?

Mohamed Hashem, the lawyer defending the survivors and relatives of those killed in Abu Zaabal, is convinced it was an attempt to cover up what he calls "first degree and attempted murder." In March 2014, a court sentenced the commanding officer, Amr Farouq, to ten years imprisonment, and three officers assigned to assist him to suspended sentences of one year - an unusual verdict in Egypt, where security personnel all too often gets away with murder. In June 2014, an appellate court judge found that Farouq had followed orders and concluded that the guilty was an “unknown person” and ordered a new investigation. This Thursday, the court is set to issue its verdict.

Lawyer Hashem told DW "this is not a fair trial" and that the presiding judges had refused to let him summon key witnesses. The incident happened inside the prison, it would be a simple matter, he said, to find the officer who fired the tear gas: "Every officer has to hand in his tear gas canister at the end of his shift to the prison authority, all you have to do is check who didn't turn it in."

Hashem said he was hopeful that Amr Farouq would be sentenced to ten years again. "If not, we will appeal again."

Back in their flat in Cairo, the grieving family of Sherif Siam did not believe they would get justice. "The trial has politicized from the start, the police officers will get off easily," his father told DW. The regime, he felt, would not let police officers be convicted. "This is a country without law," he said, shaking his head, as his wife, Iman, broke down in tears beside him. "I'm in constant pain, I can't sleep," she told DW, sobbing as she gestured to her son's picture.

"We want justice," Gamal Siam said, as he took his leave, "but even if the officer gets ten years, it won't ease the pain we're feeling."

Heba Farouk Mahfouz in Cairo contributed to this report.