And any coercion or sexual abuse that occurred, both men’s defense teams have suggested, was the result of decisions by midlevel Khmer cadres, not state policy.

The tribunal was established in 2006 to examine the effects of the Khmer Rouge’s radical policies, which historians say resulted in the deaths of some 1.7 million people.

In 2014, Mr. Khieu Samphan and Mr. Nuon Chea were each sentenced to life in prison, primarily for crimes committed during the regime’s drive to move people out of cities to work in rural communes. That judgment is under appeal, and the court has moved on to crimes at detention centers and forced labor sites, and against two ethnic minority groups.

The charge of forced marriage was included late in the development of the sprawling indictment, at the insistence of victims’ lawyers and women’s rights groups pushing for greater recognition of sexual violence and gender-based abuses in international criminal law. But the tribunal has heard evidence of the policy’s effects on men as well.

One man with broad shoulders and a deep frown, known as 2-TCCP-232, told the tribunal how he had been forced to marry someone other than his fiancée. Speaking with his head down, he recalled that they had worked in separate mobile units in the same district, digging canals and carrying dirt. But they were politically suspect because he had been a police officer, and some of her relatives had been “smashed” — taken away and presumably executed — as enemies of the revolution, he said.

A unit chief warned that he, too, would be smashed if he tried to marry his fiancée. When he was told one day in 1978 that the Khmer Rouge would arrange a family for him, he did not dare protest. A group wedding was held, in the dark, for about 50 men and 50 women.

Some, perhaps people “with good biographies,” seemed to have some say in choosing their partners, he said. But that night, he was afraid to even look at the woman he was marrying. They were couple No. 42.