The three were indicted for their attempts to suppress the student-led July-August protests last year.
The prosecutors said Hasina was also accused of mass killings, murder, and torture in a bid to suppress the uprising.
Mamun, the sole accused appearing in person, pleaded guilty when produced before the tribunal from custody, prosecutors added.
Hasina’s Awami League regime was ousted in the violent movement led by Students Against Discrimination (SAD) on August 5, 2024, following which she fled to India on a military aircraft. PTI AR GRS GRS