Two dozen people, including two women, went on trial on Tuesday for their alleged roles in the 2015 attack on Tunisia's Bardo National Museum that killed 21 foreign tourists and a police officer.

Police escorted the defendants from their jail cells to the Tunis court house, which was guarded by a security brigade with plainclothes officers inside the court room. The male defendants were handcuffed throughout the proceedings.

After a single day, the trial was expected to be postponed on the demands of several lawyers.

The March 18, 2015 attack on the famed museum outside Tunis was the opening salvo in a series of assaults in this North African country, including the slaying of 38 people, mostly British tourists, at a beach hotel. All were claimed by the Islamic State group.

The two museum attackers, who authorities said trained in a camp in neighboring Libya, were killed by security forces, but a lengthy investigation uncovered a network of helpers who allegedly provided direct or indirect support for the operation.

A dozen defendants could face death sentences if convicted of playing an active role in the attack. They are charged with voluntary homicide with premeditation. Three of the 24 defendants, who had not been held in jail, were absent from the courtroom on Tuesday.

Two women were among the accused in court, their bodies draped in traditional white Tunisian robes in keeping with courtroom procedure, their faces uncovered.

Some critics have contended that the lengthy investigation got off to a false start, with numerous people arrested but then freed later.

Investigating Judge Bachir Akremi wrote in his report that confessions obtained at the start of the investigation were obtained by torture, and some accusations against the suspects were "imaginary."

Lawyer Samir Ben Amor, who represents one of the defendants, contends that if police "had done their job correctly from the start, the attack at the Sousse (beach hotel) could have been avoided."

"Numerous people among those who prepared and planned it are the same ones implicated in the Bardo attack," he said.

Numerous lawyers have asked the court that the Sousse and Bardo attacks be judged at the same time, arguing that many defendants in each case are the same. They also wanted more time to study the voluminous file in the case.

The lawyer for the French Association of Victims of Terrorism made a written demand for a postponement to present reparation demands for families of victims — four of whom were French.

A Tunisian student who trained with Libyan militants attacked the Imperial Hotel near the Mediterranean resort town of Sousse on June 26, 2015, killing 38 people in a rampage on the beach and inside the hotel.

Some 30 suspects went on trial in May in the Sousse attack, which was suspended until Oct. 3 so that lawyers could study defendants' files.

Diplomats from Britain — which counted one victim in the Bardo attack — and France were present in the courtroom.

Authorities say strikes on tourist attractions were deliberate attempts to cripple the key economic sector for Tunisia.

In yet another attack, 12 Republican Guards aboard a bus were killed by a suicide bomber in November 2015 on the main avenue in Tunis.

Tunisia has been in a state of emergency for some 20 months.