France on Wednesday will begin the trial of 20 men accused over the so-called Islamic State group’s 2015 attacks on Paris that left 130 people dead and hundreds injured.

Nine gunmen and suicide bombers struck within minutes of each other at France’s national football stadium, the Bataclan concert hall and Paris restaurants and cafes on November 13, 2015.

Survivors of the attacks as well as those who mourn their dead are expected to pack the rooms in a secure complex embedded within a 13th-century courthouse.

The lone survivor of the extremist cell from that night, Salah Abdeslam, is the key defendant among those being tried for the deadliest attack in France since the Second World War. He is the only one charged with murder.

The same IS network went on to strike Brussels months later, killing another 32 people.

Dominique Kielemoes, whose son bled to death at one of the cafes that night, said the month dedicated to victims’ testimonies at the trial will be crucial to both their own healing and that of the nation.

“The assassins, these terrorists, thought they were firing into the crowd, into a mass of people. But it wasn’t a mass – these were individuals who had a life, who loved, had hopes and expectations, and that we need to talk about at the trial. It’s important,” she said,

Twenty men are charged, but six of them will be tried in absentia.

Abdeslam, who abandoned his rental car in northern Paris and discarded a malfunctioning suicide vest before fleeing home to Brussels, has refused to speak to investigators.

But he holds the answers to many of the remaining questions about the attack and the people who planned it, both in Europe and abroad.

The modern courtroom was constructed within the storied 13th-century Palais de Justice in Paris, where Marie Antoinette and Emile Zola faced trial, among others.

For the first time, victims can also have a secure audio link to listen from home if they want, with a 30-minute delay.

The trial is scheduled to last nine months.

September will be dedicated to laying out the police and forensic evidence. October will be given over to victims’ testimony. From November to December, officials including former French president Francois Hollande will give evidence, as will relatives of the attackers.

Abdeslam will be questioned several times. He has so far refused to talk.

None of the proceedings will be televised or rebroadcast to the public, but they will be recorded for archival purposes.

Video recording has only been allowed for a handful of cases in France considered to be of historical value, including last year’s trial over the 2015 attacks against the Charlie Hebdo newspaper in Paris and a kosher supermarket.