CAIRO (AFP) - Backers and foes of Hosni Mubarak clashed Monday as a first witness in the ousted president's trial pointed a finger of blame at the chief of anti-riot forces for dozens of deaths in Egypt's revolution. With television cameras banned inside, clashes took place outside and lawyers bickered in the heavily-guarded courtroom where Mubarak was brought in on a stretcher for the third hearing of his trial which opened on August 3. Egypt's former strongman, 83, is accused of involvement in the killings of hundreds of anti-regime activists during the 18-day revolt which in February ended his three decades in power, as well as corruption.