Shin Dong-hyuk, a North Korean defector, attends a public hearing at Yonsei University in Seoul. A U.N. panel started hearing harrowing testimony from prison camp survivors on Tuesday. (Kim Hong-ji/Reuters)

One by one they came, taking seats next to a United Nations flag and stating their names for the record. Some kept calm. Some wept. One, as he spoke, used his left hand to clamp his trembling right hand to the table.

They told stories about North Korea’s brutal network of criminal detention and political prison camps, and their evidence was physical: burns on their backs, scars on their heads, bodies ravaged by torture for acts that amount to crimes only in the North. They described forced abortions, public executions, constant hunger and ghoulish mind games played by prison guards, whose permission was needed even to catch and eat the camps’ many rats and mice.

Guards in a good mood would approve, said one defector, Shin Dong-hyuk.

Guards wanting a laugh would force prisoners to eat the rodents live.

Many of the defectors had spoken about their lives before, but this week, at a university lecture hall in downtown Seoul, their stories had a new purpose — as testimony in a U.N. investigation into North Korean rights abuses. Earlier this year, the U.N. human rights chief called those abuses unparalleled and said international attention was “long overdue” — particularly, she said, because they are continuing unabated under North Korea’s third-generation supreme leader, Kim Jong Un.

The three-member commission was established in March and given a year to complete its report. But this week-long series of public hearings in Seoul, which runs through Saturday, forms the heart of its work, a legal investigation that doubles as horrifying theater. Later in the week, the commission will also interview witnesses about other alleged North Korean rights violations, including systematic abductions of foreigners, particularly during the 1960s and ’70s.

The investigation, U.N. officials say, could help establish whether the North’s leaders are committing crimes against humanity. But in the shorter term, these hearings, streamed online, are also designed to raise global awareness of a police state that imprisons 150,000 to 200,000 of its people in city-size gulags, sealed off from outsiders in the nation’s northern mountains.

According to reports from nongovernmental organizations, the North, at these camps, gives prisoners starvation rations and works them to the brink of death, cutting back the rations further when the work is not done well. North Koreans can be imprisoned for criticizing the leadership, watching a foreign-made DVD, leaving dust on the portrait of a leader or attempting to leave the country. Many receive no trial or chance for appeal. The camps, modeled after Soviet gulags, were established by national founder Kim Il Sung as a way to weed out ideological opponents.

‘Almost as good as dead’

Witnesses on Tuesday and Wednesday said that one could be killed in the camps just for trying to stay alive. Public executions took place semi-regularly — maybe twice a year, the witnesses said — probably as a means of keeping other prisoners on edge. One camp survivor, Kim Eun-cheol, said he saw a fellow inmate executed for scavenging a potato from a field. Another was executed for eating herbs.

In both cases, the perpetrators were “almost as good as dead” from torture before their executions, Kim said. “Still, the guards used six to nine bullets to kill them.”

Jeong Kwang-il arrived at one of those camps, known as Yodok, or Camp 15, after he committed a crime and then confessed to an even greater one. As a trader in the late 1990s, he hashed out business deals with South Koreans in China — thereby associating with the enemy, under North Korean law. Confronted with evidence by North Korean security agents, Jeong at first denied their other presumption — that he was a South Korean spy.

Jeong spent much of the next 10 months hanging by handcuffs, feet suspended from the ground, in a torture position known as the “pigeon,” until he said otherwise. During that period, he lost 85 pounds, he said.

He wrongly confessed to save his life, he said.

Jeong ended up at one of the North’s largest prisons, home to about 50,000 inmates, activists say. A sign at the entrance gate says, “Let’s sacrifice our lives to protect the revolutionary leadership of Dear Leader Kim Jong Il.”

He remained there for three years, then was released, he said, after a senior guard decided he had been wrongly accused. On Wednesday, using a laptop at the folding table where he sat before the U.N. panel, he pulled up a satellite image of Yodok and described its features. He highlighted the guards’ housing facilities and the assembly hall where ideology classes were held. He described the location of the electric fence, from which sparks flew whenever it rained. He mentioned an orchard, as well as the solitary-confinement chambers where prisoners were sent if they ever tried to eat its fruit.

The commissioners mostly asked the witnesses personal questions, in an attempt to draw out their stories. But they would follow up with several clinical questions, as well, apparently seeking to establish evidence about the places and people witnesses described.

“Is this the encampment popularly known as Camp 15?” asked Michael Kirby, an Australian judge and chairman of the commission, indicating the satellite image.

“Yes,” Jeong said.

“And if North Korea were to permit an inspection, you could give us detailed information about this camp?” Kirby asked.

“Yes,” Jeong said. “I can give you exact directions.”

‘We have to talk about it’

The commissioners have tried to get into North Korea, with no luck.

The U.N. Human Rights Council, in documents issued to the media, said its officials have asked the North for “unimpeded access” and cooperation with the investigation. But those requests have been ignored.

The North often describes any discussion of its observance of human rights as a major provocation and says rights violations are impossible under its socialist system. It also denies the existence of the gulags.

The commissioners asked several witnesses this week about those denials. Kim, who was imprisoned at Yodok, mentioned that he had been forced to take a vow of secrecy about the camp before his release. Shin, who said he was born in a prison camp and escaped at age 23, said his scars were the only physical proof he could show of violations.

“But I have to tell you that something is happening there,” Shin said. “Massacres are being carried out. We have to talk about it so we can stop it. That’s why I am here.”