Pinar Selek, 51, is best known for her ground-breaking research on the Kurdish conflict in Turkey and work with street children.

An avowed feminist and prolific author, Selek was first arrested in 1998 while studying Turkey's Kurdish community, which has faced decades of persecution.

She was accused of links to the outlawed Kurdistan Workers' Party (PKK), listed as a terror group by Turkey and its Western allies.

Selek had been interviewing PKK members to find out why they had chosen armed violence. She was jailed after refusing to divulge their names to the police.

She was eventually charged in connection with a blast at Istanbul's popular spice market that killed seven people and injured dozens.

Selek was released in 2000 following the publication of a report blaming the blast on a gas leak.

But her legal problems were only starting, with a series of more trials in the highly controversial case.

She fled Turkey in 2008, settling in Germany before relocating to France, where she gained citizenship in 2017.

The presiding judge at Istanbul's main courthouse took statements from defence lawyers and urged France to extradite Selek for the next hearing on September 29.

"It is up to the French authorities to implement this," the judge said.

- Turkey's longest case -

Although her court battles began before President Recep Tayyip Erdogan's rise to power two decades ago, Turkey today is under fire from human rights campaigners for jailing activists and political foes.

"You never get used to injustice," she told AFP earlier this month.

Selek has been acquitted four times by Turkish courts -- in 2006, 2008, 2011 and 2014 -- based on a lack of evidence that the Istanbul market blast was a bomb attack.

But each time, the supreme court annulled her acquittal and ordered a retrial.

Turkey issued an international arrest warrant for Selek in January.

She faces life in prison without the possibility of parole, a sentence that could keep her from ever returning to Turkey.

Defence lawyer Martin Pradel called Selek's case unprecedented in Turkey's legal history.

"The case has been dragging on for 25 years and still the prosecution has been unable to obtain conviction," Pradel told AFP.

"A case has never lasted this long in Turkey."

The PEN International organisation promoting freedom of expression said Selek's prosecution was linked to her work as a sociologist focusing on minority rights.

It called on Turkish officials "to end their decades-long harassment of Selek and to unconditionally drop all charges against her".