One of China's most prominent human rights lawyers, Wang Quanzhang, has been put on trial in a closed court three-and-a-half years after he was detained for allegedly subverting the Chinese state.

Key points: Wang Quanzhang was one of approximately 250 legal activists arrested in July 2015

Wang Quanzhang was one of approximately 250 legal activists arrested in July 2015 Prosecutors accuse Mr Wang of representing practitioners of a banned spiritual movement

Prosecutors accuse Mr Wang of representing practitioners of a banned spiritual movement China has a criminal conviction rate above 99 per cent

The case is extremely sensitive in China, with dozens of plain clothes police blocking access to the front of the Tianjin No.2 Intermediate court and taking away at least two people who came to voice support for Mr Wang.

Three camera crews purporting to be from an outlet called Legal Online harassed a small group of Western diplomats seeking to observe the trial and called at least one Chinese member of the foreign media a "traitor".

A man purporting to be a cameraman from Chinese state outlet Legal Online films foreign journalists and diplomats. ( ABC: Steve Wang )

Mr Wang's wife Li Wenzu used overseas social media to say more than a dozen security guards turned up to her Beijing apartment to prevent her from travelling to Tianjin to attend the hearing.

She said it would have been the first time she could have been able to see her husband since his disappearance, with all previous efforts to visit him in detention denied.

According to the indictment from prosecutors, Mr Wang is accused of subverting the Chinese state by conspiring with a foreign NGO to organise training for Chinese lawyers and by representing practitioners of the banned and highly suppressed spiritual movement Falun Gong.

There was no indication from his court-appointed lawyer how he would plead prior to the trial, but the three-and-a-half-year period from arrest to court has prompted speculation that Mr Wang refused to admit any wrongdoing during his protracted period under 'residential surveillance at a designated location' in detention.

It's believed Mr Wang's judgement and sentence has already been predetermined by the Communist Party-controlled court. ( AP: Mark Schiefelbein )

Mr Wang built a career taking on some of China's most politically sensitive cases, including representing petitioners complaining about police abuses.

He was one of approximately 250 lawyers swept up in a mass crackdown in July 2015 that targeted legal activists.

While the others have all been released, tried or jailed, Mr Wang has repeatedly had his case delayed.

At least two other lawyers appointed by Mr Wang's family to represent him over the past three years were subsequently jailed, including Yu Wensheng, who has been held without trial for almost a year.

Yang Chunlin, who voiced support for Mr Wang outside Tianjin No. 2 Intermediate court, was later taken away by police. ( ABC: Bill Birtles )

Ms Li has been taking increasingly drastic steps to draw attention to her husband's case, including shaving her head and going on a 100-kilometre march from Beijing to Tianjin that was eventually stopped by police.

She and their five-year-old son have been heavily monitored, with people she believes to be from state security following them around and putting pressure on landlords, forcing them to move apartments several times.

China has a criminal conviction rate above 99 per cent and it is believed the judgement and sentence for Mr Wang's case will have been predetermined by the Communist Party-controlled court.

If found guilty, he could face anywhere from three years to life in jail.