CAIRO — An Egyptian court on Thursday acquitted a state security officer who had been convicted of torturing a detainee to death, in a case that has fueled anger over police brutality in the weeks before the 2011 uprising.

Mohamed Abdel Rahman al-Shemi had been sentenced to 15 years in prison, but Egypt’s highest civil court overturned the conviction and ordered a retrial in which he was cleared, state news agency MENA said.

Egypt’s police force is widely accused by human rights groups of abuses. The Interior Ministry says allegations of abuses are investigated.

Shemi, a major in the state security service, was one of five officers accused of detaining Mohamed Sayyid Bilal, 32, in January 2011 on suspicion that he was involved in a New Year’s Eve blast at an Alexandria church that killed at least 20.

His body was returned to his family the day after his arrest bearing signs of torture, relatives said at the time.