A Lebanese-Canadian university professor has been convicted in absentia of a bomb attack on a Paris synagogue more than 40 years ago that killed four people and injured 46 others. Hassan Diab, 69, the only person to have been accused in connection with the bomb blast outside the Copernic synagogue in 1980, where more than 300 people were worshipping, was sentenced to life imprisonment in his absence and an arrest warrant was issued against him. Diab, who has remained largely out of the public spotlight during the process, told reporters on Friday that the verdict was “Kafkaesque” and “not fair”. “We’d hoped reason would prevail,” he said after attending a vigil with supporters at the Canadian Tribute to Human Rights monument in Ottawa. He remains in Canada and did not attend the Paris trial. His legal team argued he was a victim of mistaken identity. It is not certain whether a new procedure to extradite Diab would be successful, and what tensions it would cause in relations between Canada and France. Canada’s prime minister, Justin Trudeau, said the country would “look carefully at next steps” and watch what the French government chose to do. “We will always be there to stand up for Canadians and their rights,” he said. In 2018, after Diab was released by French authorities, Trudeau suggested Canada would be skeptical of any future extradition requests. “I think for Hassan Diab, we have to recognise first of all that what happened to him never should have happened,” he said at the time. Canada’s parliament is studying a possible overhaul to the current rules surrounding extradition, which critics say give little discretion to judges. Within the country, Diab’s case is often seen as a failure of the current system of extradition rules. Diab’s lawyer, Donald Bayne, called the verdict a “political result” and a miscarriage of justice. “The evidence shows he’s innocent and yet they’ve convicted him,” he said. There were heated moments during the three-week Paris trial, where a chair was left empty for Diab. State anti-terrorist prosecutors asked for a maximum prison sentence, saying there was “no possible doubt” he was guilty. Diab’s defence asked for him to be acquitted to “avoid a judicial error”. The bombing was the first fatal attack against France’s Jewish community since the Nazi occupation of the second world war. The bomb, containing 10kg of explosive, was left in the saddlebags of a rented motorcycle parked outside the synagogue on 3 October 1980. The blast brought down the synagogue’s glass roof on those inside, who were celebrating the Shabbat and the barmitzvah of three boys and batmitzvah of two girls. A synagogue door was blown off by the force of the explosion, and shopfronts along 150 metres of road were shattered. Three passersby were killed and a concierge of the hotel opposite the synagogue died of his injuries in hospital 48 hours later. The attack was timed to hit those leaving the synagogue, and a greater tragedy was averted only because the ceremonies were running 15 minutes late. A long-running police investigation concluded that the attack, which was never claimed by any group, was organised by Palestinian nationalists. Diab, a sociology professor in Ottawa, reportedly matched a photofit of the suspected bomber. He was arrested in Canada in 2008 and extradited to France in 2014, where he spent three years in prison, some in solitary confinement, awaiting trial on charges of murder. French prosecutors claimed he was a member of the special operations branch of the Popular Front for the Liberation of Palestine, which was believed to be responsible for the attack. Each time a judge ordered his release because of a reported lack of evidence, the appeal court overruled them. Diab was finally released in 2018 and allowed to return to Canada, but in 2021 a higher French court ordered him to stand trial. The three-week trial in Paris focused in part on the discovery of a passport nearly 20 years after the attack showing entry and exit to Spain – the point from which a commando was believed to have organised the bombing. State prosecutors said the passport was “extremely incriminating”. Diab’s defence said there was no material element to prove that Diab, then a sociology student, was in France at the time. His lawyers said he had been sitting exams at a university in Lebanon and could not have used the passport, which he said he had lost.