Last Friday, 25-year-old Redouane Lakdim killed four people and injured 16 others after taking hostages in a supermarket in south-west France. It has since emerged that he was known to French intelligence services, who were concerned he was at risk of Islamist radicalisation. Lakdim himself was shot dead, but his motive for the attack shines a light on the continuing threat posed by another Islamist extremist, still being held behind bars.

Lakdim had demanded the release of Salah Abdeslam, the sole survivor from the group behind the 2015 Paris attacks that killed 130 people. Abdeslam had evaded the security services for months, but was eventually caught hiding in Molenbeek, the suburb of Brussels where he lived and grew up.

From his maximum security cell in France, Abdeslam has become infamous, receiving messages from women who want to bear his children, and numerous media interview requests. He has refused to speak, even to his lawyers, yet his silence has seen his influence grow. He appears defiant in the face of the French and Belgian justice systems, which are viewed by many black and Arab youngsters as being prejudiced against them.

In Molenbeek during the week of the hearing, I felt a degree of sympathy for him. One young man said: 'He has a point.'

The profiles of most would-be jihadis usually include some history of petty crime – Lakdim himself had drug and firearms convictions – and often some time in prison, which is where many young men have been radicalised. Abdeslam’s defiance appeals beyond the walls of his prison, to those people who have been through the judicial system or view it with distrust.

The power dynamic has changed, and everyone from the French media to the victims’ families is waiting with bated breath to see if he will break his silence and give answers about what happened on the night of the Paris attacks. Why did he not blow himself up like his older brother, Brahim, who killed himself and several others in the Comptoir Voltaire cafe, yards from the Bataclan concert hall? Was the explosive belt believed to be his, which was found in a bin, faulty, or did he change his mind?

Timeline The Paris and Brussels attacks Show Hide Paris attacks 130 people are killed in coordinated attacks in Paris at the national stadium, bars, restaurants and the Bataclan concert hall. Seven of the 10-string kill themselves or are killed: two gunmen who shot dead scores on the streets of the 10th and 11th arrondissements go into hiding north of Paris while Saleh Abdeslam flees to Belgium. He told investigators he had been supposed to blow himself up at the Stade de France but backed out at the last minute. Saint-Denis raid Abdelhamid Abaaoud, the suspected ringleader, is killed with 13 November gunman Chakib Akrouh and his cousin, Hasna Aitboulahcen, in a dawn police assault on a slum flat in Saint-Denis where he was believed to be plotting an attack on the Paris business district of La Défense Brussels shootout Four police are wounded and an Algerian suspect killed in a gun battle at at an apartment in the Forest suburb of Brussels, where Abdeslam had been hiding. He escapes over the rooftops. Abdeslam arrested Abdeslam is captured in a raid on an address in the Molenbeek area of Brussels close to his family home. Belgian authorities say he told investigators he was planning a fresh attack in the capital. Brussels attacks Coordinated suicide attacks at Brussels airport and on the metro system kill 32 people. The bombers include Najim Laachraoui, named the previous day as a suspect in the Paris attacks, possibly as the bombmaker, and Khalid el-Bakraoui, who was also suspected of playing some kind of logistics role in the Paris attacks. Suspect arrested An alleged surviving member of the Brussels attackers, Mohamed Abrini, is arrested in Brussels. Investigators said he confessed to being the third man caught on video with suicide bombers at Brussels airport. A childhood friend of Abdeslam, he was also filmed driving a Renault Clio days before it was used in the Paris attacks.

Yet if young men are attracted to jihadism because it feels thrilling and violent, like something out of a movie, then Abdeslam’s story has dangerous potential for at-risk youth. He has fashioned himself into the ultimate antihero, a prisoner of the state appealing to his community on the outside. His choice of words makes him even more dangerous. In court last month, he spoke only to say that his silence was his form of defence.

“What I observe is that Muslims are judged, treated in the worst of ways,” he said. “They are judged mercilessly. There is no presumption of innocence, there is nothing, we’re immediately guilty, voilà. My silence does not mean that I am guilty: it is my defence.” In just a few sentences, Abdeslam elevated himself from a deluded criminal to a potentially dangerous spokesman for disillusioned young Muslims across Europe. He finished by saying: “Judge me, do what you want to do. I place my confidence in Allah. I have not fear of you.”

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Sven Mary, Abdeslam’s lawyer in Belgium, referred to his client as “stoic”. Journalists in court scoffed at this description, but Abdeslam’s performance wasn’t for their benefit. In Molenbeek the week of the hearing, I felt a degree of sympathy for him. One young man said to me: “He has a point.” Others told me they didn’t believe the system would allow him a fair trial.

The French and Belgian authorities must not confirm these prejudices. Abdeslam’s story is being watched around the world, and the process needs to be seen as being completely fair, upholding justice and showing that European courts hold the moral authority.

Nicolas Hénin was kidnapped in Syria in 2013 by a group of Islamic State fighters that included two members of the group of British nationals known as “the Beatles”. When they were arrested last month, Hénin was vocal about how a fair trial was essential to prevent further radicalisation. He’d experienced first-hand anger fuelled by images of Guantánamo Bay detention camp.

“Why do you think [our captors] put us in these stupid orange jumpsuits? Why do you think they waterboarded some of us? It’s because they were mocking Guantánamo,” said Hénin. “Guantánamo was actually one of their reasons for their engagement in extremism and jihad, so if we perpetrate this kind of atrocity, we are not helping our quest for justice.”

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Given such a difficult figure as Abdeslam, it can be hard to ensure justice is seen to be done by even the most disillusioned of watchers. There has never been a case like this. But as last Friday’s attack shows, we cannot get it wrong. We cannot allow Abdeslam to build himself into a living martyr, to use his platform to speak for frustrated young Muslims, or inspire them to strike in his name.

Abdeslam may not give us the answers we are looking for, but we already know that there is a real problem among some disillusioned youngsters across Europe. These young men are often not particularly religious, but have limited prospects, and live on the fringes of society. We need to find a way to bring them back into mainstream society and away from the messages peddled by Isis. That means building trust between communities, police and the justice system. We must not let him be the most prominent voice, even in his silence, appealing to those who feel angry, violent or lost.

Abdeslam’s trial on terror charges over the Paris attacks will not begin in full until 2019; but whatever the final verdict, if things continue as they are, he will remain a threat, and a symbol for all those whose aim is to pitch Muslims against the west.

• Iman Amrani is a Guardian multimedia journalist