Egypt's Court of Cassation has accepted a retrial in the Abu Zaabal prison van case, where four policemen face accusations of involvement in the deaths of 37 prisoners in 2013.
The general prosecution had filed an appeal with the court after an initial appeal in June 2014 overturned a 10-year prison sentence handed down to one policeman and a one-year suspended sentence given to three others on charges of killing 37 prisoners inside a police van.
The four policemen stand accused of involuntary murder.
On 18 August 2013, the interior ministry said that 37 supporters of ousted president Mohamed Morsi arrested in protests had died of asphyxiation due to teargas and overcrowding while being transferred to Abu Zabaal Prison in Cairo in a police van.
Policemen Amr Farouq, Ibrahim El-Morsi, Islam Abdel-Fattah and Mohamed Abdel-Aziz were all convicted in the original trial.
Security forces initially claimed the prisoners had died during an escape attempt. However, prosecution investigators said there had been no escape attempt.
Egyptian police have long been accused of using excessive force and torturing detainees. The January 2011 uprising, which led to the ouster of Hosni Mubarak, had its origins in a protest against police brutality.