Under the terms of a judicial co-operation agreement with Chad, they were repatriated to France where they are expected to serve normal prison sentences as French law does not allow forced labour.
The state prosecutor in the Paris suburb of Creteil called for an eight-year prison sentence.
"The most suitable sentence would be eight years in prison," Jean-Jacques Bosc told the court, convened to convert the hard labour sentence.
He said Monday's hearing was a purely technical procedure.
|The workers were trying to fly 103 children from |
Chad to place in European foster care [AFP]
"We are not holding a new trial here. You cannot reconsider the facts or revise the sentences. Taking this path would be to violate an international principle," he said.
But a new trial is exactly what defence lawyers want.
They said before the hearing opened that the Chadian sentences were not valid because they were imposed in what they described as an undemocratic state and after a trial which they said was not fair.
The Creteil criminal court said it would hand down a ruling on January 28.
The aid workers were arrested in October as they tried to fly 103 children, aged one to 10, from eastern Chad to Europe for fostering with families there.
They said they had been on a humanitarian mission to rescue orphans from Sudan's war-torn Darfur region, across Chad's eastern border.
But most of the children were found to have come from families in Chadian border villages who gave them up on promises of education and healthcare for the boys and girls.