Fourteen people are on trial in France over the deadly attack on the satirical magazine Charlie Hebdo in 2015, reports BBC News.
Most of the alleged accomplices are in court in Paris, but three are being tried in absentia.
They are accused of helping the militant Islamist attackers who shot dead 12 people in and around Charlie Hebdo's Paris office in January 2015.
In a related attack, a third gunman shot dead a policewoman, then attacked a Jewish store, killing four people.
The 17 victims were killed over a period of three days. All three attackers were killed by police. The killings marked the beginning of a wave of jihadist attacks across France that left more than 250 people dead.
In the days following the January 2015 attacks, millions of people took part in solidarity marches across France and around the world under the slogan "Je suis Charlie" (I am Charlie).
The magazine has marked the start of the trial by reprinting controversial cartoons of the Prophet Muhammad that sparked protests in several Muslim countries.
President Emmanuel Macron has since defended the freedom of the press and the French "freedom to blaspheme, which is linked to freedom of conscience".
Eleven of the defendants were present in the courtroom on Wednesday. They gave their names and occupations, and all confirmed they intended to answer questions from the court.
Survivors and relatives of the victims were also in court. Gala Renaud, the wife of one of the journalists killed, told reporters that you could "already feel the tension".
"I wanted to see the defendants in the box to see what they look like," she said, adding that she wanted to know "what their motivations were, why this complicity and of course why innocent people were killed".
The trial has been delayed by almost four months because of the coronavirus pandemic. In March, the presiding judge said France's lockdown measures had made it impossible to bring together "all the parties, witnesses and experts under the necessary sanitary conditions".
The alleged accomplices are accused of obtaining weapons and providing logistical support for the attack on Charlie Hebdo's office on January 7th 2015, as well as the subsequent attacks on a police officer and the Hyper Cacher supermarket.
Three of the suspects are believed to have disappeared in northern Syria and Iraq and will be tried in absentia. Some reports suggest at least two of them were killed in bombing campaigns against the Islamic State group (IS). All three remain the subject of international arrest warrants.
There are about 200 plaintiffs in the trial and survivors of the attacks are expected to testify.