A judgement is due in a French court case against the managers of a company that made substandard breast implants.
Jean-Claude Mas and four of his former colleagues are accused of aggravated fraud, following the collapse of Poly Implant Prothese (PIP).
PIP implants were found to contain industrial silicone and have an increased likelihood of bursting and seeping.
It has been estimated more than 300,000 women were affected by the faulty implants in 65 countries.
It is thought around 47,000 British women were given the implants.
The case against Mas has more than 5,000 women registered as plaintiffs and was heard in a conference centre in Marseille instead of a court to allow enough room.
Among the women who gave evidence was Jan Spivey from London, who was given PIP implants as part of reconstructive surgery following treatment for breast cancer.
She blames them for subsequent health problems and told Sky News: "The symptoms were so overwhelming to deal with.
"They impacted on my everyday life. I'm very frightened about the future."
Mas, 73, has pleaded guilty to fraud, but denies the more serious charge of aggravated fraud, which in French law involves a deception that creates a health risk.
During the hearing, the PIP founder was compared to a "mad chemist". If convicted he could be jailed for up to five years.
Tracey Ahmet is among the British women who were given PIP implants.
Speaking to Sky News ahead of the ruling, she said: "If he doesn't go to jail it will send us all over the edge. I think we'll all have a breakdown.
"If I took anything from the kitchen sink and injected it in somebody, I'd be in prison by now. He's done it to thousands and thousands of women."
Despite a decision from the French government two years ago that women should have PIPs removed as a precaution, a review in the UK ruled it was not necessary.
Later, women who had been given the faulty implants on the NHS were told they would be removed and replaced.
The Welsh government also agreed to pay for removal and replacement, even for women who had the procedure privately.
A review by NHS medical director, Sir Bruce Keogh, which was ordered after the scare, called for tougher controls on the cosmetic surgery industry.
The Department of Health is still to respond to his recommendations.
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