Former judge Mahmoud El-Khodeiry was arrested in Alexandria late Monday, reported the Middle East News Agency (MENA), on accusations of inciting torture, according to one of the defendant's lawyers.
Muslim Brotherhood members Hazem Farouq, Mohamed El-Beltagy and Islamist figure Safwat Hegazy are accused in the same case of conducting the torture of lawyer Osama Kamal Mohamed in Tahrir Square.
A large number of Brotherhood figures have been arrested since the ouster of Islamist president Mohamed Morsi on 3 July. Many face accusations of inciting violence.
Prosecution ordered El-Khodeiry's arrest after he had been repeatedly summoned for questioning but failed to make an appearance. He will be transferred to Cairo where the trial is currently being held.
The former deputy head of the appeals court, El-Khodeiry was a leading figure in the movement demanding the independence of the judiciary in 2005-2006 under ousted president Hosni Mubarak.
El-Khodeiry was also elected MP in the post-Mubarak parliamentary elections in 2011.