PARIS — THE cluster of Roma, handcuffed and caged-in behind glass walls, listened in silence as prosecutors accused them in court of selling child brides for up to about $270,000 in cash, valuing them based on their ability to steal. In a case that has riveted France, the prosecutors accused three family clans from Croatia of grooming girls and boys as young as 11 to steal as part of a gang that committed 100 robberies in France, Belgium and Germany in 2011.

One 20-year-old witness told the court he had stolen about $600,000 in cash and jewels for his parents, or more than $7,000 a month, since age 13. Less skilled thieves could face punishment, including beatings by Roma elders.

All but one of the 27 accused were convicted on Oct. 11 in Nancy, in eastern France, of forcing the children to steal, and received sentences from two to eight years. At the top of the network was a 66-year-old grandmother.

The case highlighted an increasingly rancorous debate here and across Europe about what some politicians call, rather ominously, the “Roma question,” a reference to the nomadic people, also known as Gypsies, who came from India to Europe centuries ago. An estimated 11 million are scattered across Europe.