Former Egyptian president Hosni Mubarak returned to court for a fourth hearing in his trial on charges of corruption and complicity in the killing of protesters during the 18-day-uprising that toppled him. (AP)

Egypt’s military rulers were summoned to testify at the trial of their former commander, Hosni Mubarak, on Wednesday after police witnesses dealt prosecutors another blow by refusing to implicate Egypt’s longtime leader in the deaths of protesters.

Judges ordered Field Marshal Mohammed Hussein Tantawi — the head of the military council ruling Egypt — and some of his top deputies to testify in a closed session of the former president’s trial on charges of corruption and complicity in the deaths of protesters, according to state TV.

The extraordinary step of hauling in the powerful army heads could help lend force to a trial that has disappointed those who hold Mubarak responsible for the more than 900 deaths that took place in the 18 days of protests. Many Egyptians think that Tantawi holds the key to whether Mubarak personally gave orders. But the closed sessions, which will start Sunday — seven months to the day since Mubarak stepped down — will keep the public from knowing what the top officials say.

Tantawi and the army forced Mubarak to step down after they sensed he had lost control of the country, and a popular chant in the early days of post-Mubarak Egypt was “the people and the army are one hand.” But popular frustration with their rule has mounted. Tantawi’s testimony about the man who was his boss for decades and made him the head of the army will be a crucial test of the depths of their break.

Judge Ahmed Refaat also issued a gag order preventing media coverage of the closed sessions, though the practical effect of trying to prevent media outlets from covering what is sure to be a focus of popular fascination is unclear in an era when so many self-publish on Twitter, Facebook and blogs.

On Wednesday, a police captain became the latest witness to deny that Mubarak had anything to do with the deaths of protesters — because on the deadliest day of the protests, riot police weren’t armed with live ammunition, the captain said, according to lawyers. Prosecutors charged him with perjury, and Refaat had him detained, though he was acquitted at the end of the session.

The captain, Mohammad Abdel-Hakim, had previously signed an affidavit saying that he had issued live ammunition to the forces under his command. Other witnesses on Monday told stories similarly at odds with the affidavits they had sworn to, all to the effect of making the shootings of protesters appear more spontaneous and less premeditated.

Some Egyptians are deeply worried that Mubarak won’t be convicted of any charges.

“I’m sure he’ll be acquitted,” said Alaa Zaghlol, 28, an accountant who was carrying a poster depicting Mubarak’s head inside a noose in front of the courtroom Wednesday. “The judicial system is corrupt, politicized and loyal to the old regime,” he said.

Mubarak’s 29-year domination of Egyptian institutions means that he is on trial before a panel of judges whom he had appointed and is being prosecuted by lawyers whom he once approved.

In addition to Tantawi, the top officials who will testify in the closed sessions next week — Armed Forces Chief of Staff Sami Anan, former vice president Omar Suleiman, former interior minister Mahmoud Wagdy and current Interior Minister Mansour el-Eissawy — also have ties to Mubarak. Then again, so does almost all of the ruling class.

Activists have called for a large protest in Tahrir Square on Friday, which they have dubbed “Correcting the Path,” demanding for an end to military trials of civilians and a concrete timeline for a handover to civilian rule. In a proclamation issued on the ruling military council’s Facebook page Wednesday, it called any attack against the military “a threat to Egyptian national security and this great people.”

Special correspondent Ingy Hassieb contributed to this report.