Four men already had been convicted of murder in southeastern China when a fifth person confessed to the crime. But when lawyers demanded to review case documents to clear the men's names, the court stonewalled. So the lawyers unfurled banners outside the venue.

They protested for days, alongside social activists who insulted the top judge, and uploaded pictures online.

The incident in the southeastern province of Jiangxi in May appears to have been one of the last straws ahead of a broad crackdown by China's Public Security Ministry on a category of lawyers who have come to be known as "rights defenders."

Authorities say these lawyers have strayed far beyond their professional role into illegal activism aimed at sabotaging the country's legal system. The lawyers maintain their methods are merely to hold authorities to account and ensure that the letter of China's laws is upheld.

Since late May, police across China have detained and called in at least 215 rights lawyers and social activists, most of them during the past week or so. State propaganda has kicked into high gear to denounce them as rabble-rousers, criminal gangs, profit-seeking opportunists.

Some even face the severe charge of inciting to overthrow state power.

Foreign governments and human rights groups have condemned the crackdown, seeing it as Beijing's iron-fisted response under President Xi Jinping to any growth of civil society that could challenge the Communist Party's authoritarian rule. It also shows that the rights lawyers have gained enough influence with the public to make Beijing uneasy, joining outspoken bloggers and activist movements in drawing crackdowns since Xi came to power in 2012.

"They are the most important and active force in China's pursuit of political democracy," said Teng Biao, a visiting scholar studying China's law and human rights issues at Harvard University and New York University. "The public support for them is growing. They have the abilities to organize, to effectively make political appeals and to take action, and they are seen by the authorities as a threat to their political security."

In the 1990s, only a handful of Chinese lawyers were gutsy enough to challenge authorities by representing clients persecuted by the government, such as practitioners of the banned spiritual group Falun Gong. These lawyers, who believed in individual rights and insisted that the law must be obeyed, attracted public attention in the early 2000 with several public interest cases. A regional news magazine highlighted 14 of them in 2005.

Their ensuing growth in number coincided with the rapid rise of social media, which have facilitated bonding among like-minded lawyers across the country. Through online communication tools, they have found camaraderie and mutual support. They share experiences and collaborate on major cases, as they grapple with hostility and obstruction from authorities.

Occasionally some of them were arrested, but the group continued to grow to from an estimated 200 practitioners to 300.

"They are a bit different from other lawyers in that they are willing to confront the state over cases deemed sensitive," said Eva Pils, a legal scholar at the King's College London who follows Chinese lawyers closely.

They are among the most vocal attorneys in China's social media, seeking public support both as leverage to improve the legal climate and as an insurance of their own protection.

"The odds are stacked so much against them that they have no choice left but to go to the public," Pils said.

Rights lawyers have found themselves barred from meetings with their clients, and rebuffed in attempts to throw out confessions obtained through torture. When they get thwarted in court, they take to the street.

"They are using these methods to say the government is not following the law and to put pressure on the government," Pils said.

Along the way, the lawyers have become a rallying point for social activists, people with grievances and those facing persecution — forming a formidable force that has alarmed the authorities.

In early May, they managed to raise doubts when a police officer fatally shot an unarmed but irate farmer inside a train station in northeastern China.

Grassroots activist Wu Gan was able to obtain an independent video clip showing the police officer beating the man, raising questions whether the police officer had unnecessarily provoked him. Authorities later were forced to release additional security footage showing the man becoming violent and out of control, though public doubts about the incident lingered.

This loose alliance also has pooled and raised money to pay for costs of activism, such as transportation, and in some cases to subsidize the lives of people who have been persecuted. Wu himself was employed by the Beijing-based Fengrui law firm. Both Wu and many of Fengrui's lawyers have been arrested in the crackdown.

Authorities argue that the financial backing has created a professional class of rabble-rousers for whom the details of a legal case take a back seat to creating publicity and causing trouble.

"For some people, this is their livelihood," according to a June report by the official Xinhua News Agency. "Regardless of the facts of any given case, they always travel to voice support and spread the information via overseas websites. Their purpose is to create some international influence to put pressure on local governments and to interfere with the legal process."

Following the police shooting, Wu turned his attention to the high court of Jiangxi, where the five lawyers were demanding to review court dockets of the murder case but got stonewalled.

The lawyers — not members of Fengrui — were representing four men they believe were wrongfully convicted of murder in the May 2000 deaths of a convenience store owner and an accompanying woman. In 2012, a fifth man confessed to the crime, yet the court has not made any move to review the case.

When the lawyers traveled to Jiangxi in May, they were denied access. For days they protested and uploaded photos of their demonstrations. They unfurled banners and held a candle vigil to deplore what they called judicial wrongdoing.

Wu joined them and called the chief of the provincial high court a rogue and planned a mock funeral ritual for him. Wu later was arrested on the charges of provoking troubles and, far more seriously, inciting to overthrow the government. State media have denounced his methods as insulting and illegal, though Wu has insisted they are nonviolent and within legal boundaries.

Barely two months later, the law firm he worked for was raided by police, and its key attorneys were taken away on suspicion of running a major criminal gang.

"The state media's 'expose' on the lawyers is meant not only to discredit one law firm or its lawyers — it is meant to smear the mode of operations of an entire rights defense movement, one that has been used rather successfully for years to make the government somewhat more accountable," said Maya Wang, a researcher for Human Rights Watch.