Thirst, cigarette smoke and a precarious stack of plastic stools.

Those are some of the weapons state-security agents used in an effort to extract a confession from Xie Yang, a Chinese human-rights lawyer, according to a transcript of his chilling and unusually comprehensive account to his lawyers in a series of jailhouse meetings. Mr. Xie was detained in 2015 and is due to soon face trial on subversion charges.

“I’m going to torture you until you go insane,” Mr. Xie quoted one of his interrogators as saying, according to the lawyers’ notes. “Don’t think you’ll be able to continue being a lawyer once you get out. You’re going to be a waste of a person.”

The transcript, dated early January, began circulating online on Thursday. Chen Jiangang, one of the two lawyers named on the document, confirmed its authenticity to China Real Time, saying Mr. Xie’s legal team made the decision to release it publicly once it became clear that their client wouldn’t be let out for the Lunar New Year holiday, which starts next week.

The transcript offers the first detailed account of time spent in police custody by one of several lawyers who were detained in a sweeping government crackdown on human-rights activists in July 2015. Some of those lawyers have been released on China’s equivalent of bail after appearing in video-taped confessions, but none have opened up at length about their detentions.

The use of torture to extract confessions is commonplace in China, lawyers and human-rights group say, and many of the techniques Mr. Xie described to his lawyers have been previously documented in reports by groups like Amnesty International and Human Rights Watch. Lawyers and activists said Mr. Xie’s account is nevertheless striking for its clarity, and for how it illuminates the territory Chinese authorities are willing to tread in their campaign against lawyers they see as threatening.

“These are things I’ve come across many times before, but it shook me to hear him describe them so clearly,” said Mr. Chen. “This is the first time I’ve heard of a political case where a lawyer has been tortured in this way.”

Chinese government has said it will punish anyone who uses torture to extract confessions, which is prohibited by law. The government has said the arrested lawyers’ cases have been handled according to law.

The details in the transcript resonate all the more after another human-rights lawyer, Li Chunfu, emerged from nearly 17 months in police custody in what those around him characterize as a shattered state. Family members have said in public statements that Mr. Li has suffered violent bouts of paranoia since his release on Jan. 12 and was recently diagnosed with schizophrenia.

“Li Chunfu is broken. He can’t tell the story of what happened to him,” said Kit Chan, executive director of the Hong Kong-based China Human Rights Lawyers Concern Group.

A photo taken on Dec. 26, 2016 shows the city of Changsha in central China's Hunan Province. Chinese human rights lawyer Xie Yang told his lawyers that he was taken to a Changsha hotel room and tortured in 2015 as part of a crackdown on dissent. Photo: Zuma Press

Based in central China’s Hunan province, Mr. Xie divided his time between commercial law and defending activists detained in the government’s various crackdowns, according to human-rights groups. He also represented the family members of a petitioner who was killed in a controversial police-shooting case in northeast China.Several of those who looked into the government’s handling of that case became early targets in the crackdown on human-rights lawyers.

According to the transcript, Mr. Xie was detained by police at a hotel in central China’s Hunan province in the early morning hours of July 11, 2015. Soon after, he was transferred to a hotel in the Hunan capital of Changsha for what is known as “residential surveillance in a designated location” -- a form of incommunicado detention that the United Nations’ Committee Against Torture criticized in a report last year for putting detainees at “high risk” of ill-treatment.

For seven days, the transcripts says, Mr. Xie faced near round-the-clock interrogations by rotating teams of state-security agents. He was never allowed to sleep for more than three hours at a time, and was routinely deprived of water.

Interrogators wanted Mr. Xie to renounce membership in a human-rights lawyer chat group that they believed was a political organization, but which Mr. Xie told them was just a platform to exchange information, the transcript says. They also wanted him to account for why he had taken on various cases, including the police shooting.

“For any action you’ve taken, you have a choice of three motivations: either you did it for fame, for profit, or because you’re anti-Party and anti-Socialism,” the transcript quotes a lead interrogator as saying.

When Mr. Xie refused to attribute his actions to one of those choices, the agents responded by blowing cigarette smoke in his face, and punching and kicking him in the stomach out of view of a video camera.

In the most persistent torture, known as "the dangling chair," Mr. Xie was forced to answer questions while sitting on a wobbling stack of backless plastic stools that left his feet dangling above the ground. If he fell off balance or moved in other ways, his interrogators would accuse him of attacking them and beat him, he told his lawyers.

A portrait of Chinese lawyer Xie Yang by political cartoonist Badiucao. Photo: Courtesy of Badiucao

“I sat there, with my feet dangling, for 20 hours every day. At first my legs would hurt, then they’d go numb. Later they swelled up,” the notes quote Mr. Xie as saying. The agents also threatened his family, he said, suggesting his child or wife might get hurt in a traffic accident

Eventually, the lawyer collapsed under the pressure and began signing statements presented by the agents, according to the transcript. He later contemplated suicide, he said.

Prosecutors accuse Mr. Xie of attempting to subvert state power by promoting negative views of the government online, by working with unnamed antigovernment forces in China and abroad, and by manipulating people “who did not know the facts” to resent the government, according to a copy of the indictment seen by China Real Time.

Mr. Xie’s lawyer, Mr. Chen, said his client signed statements in which he admitted making mistakes but that he never admitted to committing any crime. Mr. Xie told his lawyers that he signed the statements under immense distress and that they weren’t accurate.

“It was a situation worse than death. I can’t describe it. By the third day, I’d fallen apart. My spirit was completely crushed,” Mr. Xie said, according to the statement.

Mr. Xie’s legal team is in the process of filing charges against the agents the lawyer says tortured him, Mr. Chen said. The Changsha Public Security Bureau and prosecutor’s office didn’t respond to requests for comment. Calls to the Changsha No. 2 Detention Center, where Mr. Chen said he met with his client, rang unanswered Friday.

What makes Mr. Xie’s testimony unique, said Ms. Chan of the China Human Rights Lawyers Concern Group, is its proliferation of names and dates. “If you say it’s just the word of one man, then let’s have a third-party investigation,” she said.

An English-language translation of the first part of the transcript is available here.

NOTE: An earlier version of this post translated the Chinese name for the torture that involves forcing detainees to sit still on a high stack of plastic stools as "the hanging chair." It has been updated to use the more commonly recognized translation, "dangling chair."

-- Josh Chin. Follow him on Twitter @joshchin