PHNOM PENH, Cambodia (AP) — The U.N.-backed tribunal trying members of Cambodia’s former Khmer Rouge regime for genocide and other crimes turned its attention Tuesday to forced marriages, with witnesses testifying how such bonds were supposed to serve the state rather than personal wishes.

The defendants — Khieu Samphan, 85, head of state in the 1970s regime, and Nuon Chea, 90, right-hand man to the communist group’s late leader, Pol Pot — already received life sentences in 2014 after being found guilty of crimes against humanity. Some 1.7 million people are estimated to have died from starvation, disease and execution as a result of the group’s extremist policies.

Charges against the defendants in their second trial include genocide against ethnic minorities, along with implementing policies of rape and forced marriages.

Two witnesses testified Tuesday how they were ordered to marry and were spied upon by the Khmer Rouge to make sure they consummated the relationships. Both testified about their fear of being killed if they did not cooperate.

One witness, 77-year-old Sour Sotheavi, said he and the woman he was forced to marry agreed that for their own safety they would have to have sex once. He said he never had sex again with her — or anyone else — in part because he was always exhausted from his daily work of breaking rocks.

He said his marriage was part of a mass ceremony of 107 couples who had to make a vow to “Angkar” — as the Khmer Rouge were known to ordinary people — and pledge to produce children as Angkar required.

Youk Chhang, head of the Documentation Center of Cambodia, which has collected more than a million documents related to the Khmer Rouge terror, told The Associated Press that the victims of the Khmer Rouge were dehumanized, a policy that extended to marriage.

“Couples were merely elements for procreation of the work force for the Khmer Rouge revolution,” he said.

In cases where both parties were Khmer Rouge supporters, marriage might have been arranged rather than forced. Prime Minister Hun Sen, a Khmer Rouge officer who later defected from the group and led a Vietnamese resistance force against it, was married in this manner. His wife Bun Rany was the director of a Khmer Rouge hospital.

But for most people, especially women, there were few options.

“It was the Khmer Rouge policy even before they took power in 1975,” said Youk Chhang. “Women then were forced to marry Khmer Rouge handicapped combatants to glorify the revolution and encourage men to go to the battlefields. Many women fled the Khmer Rouge liberated zones or their entire families ended up being punished if they disobeyed the order.”