She was sold off 12 times in 10 years by pimps, but when a young Serbian sex worker testified in a French court, defence lawyers told her not to "exaggerate".

Her case, cited by an anti-prostitution activist, is just one example of why so few sex workers dare speak out at pimping trials in France for fear of stigma, reprisal, pressure or just because they want to draw a line under their traumatic past.

This, experts say, makes the "aggravated pimping" trial involving Dominique Strauss-Kahn all the more unusual, as ex-prostitutes have dared to take the stand with graphic descriptions of their orgies with the former International Monetary Fund chief, who denies knowing they were sex workers.

But while this trial is taking place under the media spotlight due to the presence of Strauss-Kahn as one of the 14 accused, it is but one of around 400 aggravated pimping court cases in France every year, says Yves Charpenel, a magistrate at France's highest appeals court and head of an anti-prostitution foundation.

"In these cases, only one victim in 100 will come testify in court."

Those who accept to take the stand "are those who have turned the corner, 'survivors' who say 'I have nothing to lose anymore'," he says, lauding the bravery of those testifying in the northern city of Lille.

- 'My mum reads it' -

Prostitution in itself is legal in France but procuring -- the legal term for pimping which includes encouraging, benefiting from or organising prostitution -- is a crime.

And when it comes to pimping trials, many of those who could testify just want to draw a line under their difficult past.

"We're talking about sexual violence, the victims are ashamed, they want to turn the page, forget what they experienced," says Gregoire Thery of the Mouvement du Nid group that acts for those who are involved in prostitution.

Along with another association, the group is currently supporting the prostitutes who are both witnesses and seeking compensation in the Lille trial involving Strauss-Kahn.

The women often fear that their friends and family will find out what they do, as the court cases are usually public and can reveal a part of their lives they had painstakingly covered up.

That's the case for Jade, one of the former prostitutes testifying in the Lille trial, whose family was not aware of what she once did.

Weeping, she told the court that "the difficulty is that everything I say is transcribed in the press, and my mum reads it."

Thery says it is also hard for those who appear in court to apply for a job when they are plagued with the spectre of their former activities.

"They are scared that their testimony will harm them for the rest of their life."

Charpenel adds that they must also be supported psychologically and financially during the trial, and often years before.

Many also need administrative help, and particularly those who are foreign, often have no ID and represent the majority of victims of procuring in France.

- Sold 12 times in 10 years -

And even if they have talked to the police during a probe, sex workers baulk at having to stand trial for fear of authorities but also of coming face to face with those who controlled them.

They also face huge pressure, says Charpenel.

"If they are foreign, the pimps have a hold over them through their families back home," he adds, citing the example of a young Romanian girl whose little boy was kidnapped by pimps to stop her from talking.

But for Thery, that's nothing compared to the pain for women who often suffered violence, trauma and loss of being told by defence lawyers or magistrates that they "got something out of it".

"There is an underlying idea that these girls made money prostituting themselves, and that now they want more from the trial," says Christophe Grignard, a lawyer for the EACP association that fights procuring.

"They are told horrendous things, that it's a love story gone wrong, that they are exaggerating their suffering," adds Charpenel.

When they testify, though, the pimps are often sentenced more severely, he says.

"Judges need to see it to believe it."