The family of a Syrian soldier has brought civil proceedings before a French criminal court after it claimed to have recognised an French Islamic State (Isis) convert who slit the throats of captured Syrian pilots on an IS video released last year.

On 24 September, the Chamber of the Court of Appeal of Paris allowed for the Syrian family to join the criminal prosecution as a civil party, describing its registration as "admissible", according to Le Monde.

The Syrian family, who comes from Homs, has joined the prosecution in the case of Maxime Hauchard (now known as 'Abu Abdahhah' or 'al-Faransi', which translates as 'The Frenchman') after it claimed its son is one of the 18 captured Syrian pilots killed in the jihadists' video released in November 2014.

12 Syrian soldiers decapitated

Hauchard, a former cinema lover and pizza delivery man from suburban Normandy, and another French man, Mickael dos Santos, were identified as part of a group seen cutting the throats of 18 captured Syrian pilots in the 15-minutes film.

The video shows the jihadists – including British Islamic State fighter"Jihadi John" – making their victims kneel before them, then slitting their throat. The IS fighters then showed the severed head to the camera before resting it on the back of the mutilated corpse.

After the video was broadcast, a judicial investigation was opened against Hauchard and Dos Santos for crimes committed by an organised group and for criminal association in relation to a terrorist undertaking.

Because the video images showed the Syrian family's son is not a direct victim of Hauchard, but that of one of his peers, the investigating judge has first refusal to accept the family's application to conduct a civil action within the criminal proceedings. At the time, the magistrate had declared that it was impossible to confirm the identity of the dead soldier.

The Syrian family subsequently appealed his decision and won. The court added that new images it received were sufficient evidence to establish "the true formal recognition" of the family's son.

Lawyer has strong links with Syria

Lawyer Fabrice Delinde has been representing the Syrian family, and has travelled to Syria on a number of occasions to obtain the family's trust.

The French media, however, have pointed out that Delinde – who is closely linked to France's right-wing Front National party – has been a long-time supporter of a dialogue with Syria's president, Bashar Al-Assad.

Commentators have questioned the neutrality of Delinde's undertakings after it was revealed he was part of a group of lawyers who travelled to Syria in October 2013. On his return, Delinde sent an open letter to president Francois Hollande, asking him to "reconsider" his position vis-à-vis Al-Assad's regime.

Through these proceedings, the media claim Delinde hopes to put the question of French co-operation with Syria back on the table.

Delinde represented one of the four men charged in January for allegedly helping Paris Kosher supermarket hostage killer Amedy Coulibaly.