HONG KONG (AP) — Jimmy Lai, a former newspaper publisher and one of Hong Kong’s most prominent pro-democracy activists, spends around 23 hours a day in solitary confinement in a maximum-security facility while he awaits a trial that could send him to prison for life.

In exclusive photos taken by The Associated Press in recent weeks, the 75-year-old Lai can be seen with a book in his hands wearing shorts and sandals and accompanied by two guards at Stanley Prison. He looks thinner than when he was last photographed in February 2021.

Lai is allowed out for 50 minutes a day to exercise. Unlike most other inmates, who play football or exercise in groups, Lai walks alone in what appears to be a 5-by-10-meter (16-by-30-foot) enclosure surrounded by barbed wire under Hong Kong’s punishing summer sun before returning to his unairconditioned cell in the prison.

The publisher of the now-defunct Apple Daily newspaper, Lai disappeared from public view in December 2020 following his arrest under a security law imposed by Beijing to crush a massive pro-democracy movement that started in 2019 and brought hundreds of thousands onto the streets. More than 250 activists have been arrested under the security law and vanished into the Hong Kong legal system.

Photographers used to be able to catch a glimpse of activists in remand at another detention center in Lai Chi Kok as they were taken to and from court. Authorities started blocking this view in 2021 by making the detainees walk through a covered pathway.

In a separate case, an appeals court is due to rule Monday on a challenge that Lai and six other activists have had filed against their conviction and sentencing on charges of organizing and taking part in an unauthorized assembly nearly four years ago. The others are Lee Cheuk-yan, Margaret Ng, Leung Kwok-hung, Cyd Ho, Albert Ho and Martin Lee.

Lai, a British national, is accused of colluding with foreign forces to endanger national security and conspiring to call for sanctions or blockades against Hong Kong or China. He also faces a charge of conspiracy to print seditious publications under a colonial-era law increasingly used to crush dissent.

He was scheduled to go on trial last December, but it was postponed to September while the Hong Kong government appealed to Beijing to block his attempt to hire a British defense lawyer.

“My father is in prison because he spoke truth to power for decades,” Lai’s son, Sebastien, said in a May statement to a U.S. government panel, the Congressional-Executive Commission on China.

“He is still speaking truth to power and refusing to be silenced, even though he has lost everything and he may die in prison,” Sebastien Lai said. “I am very proud to be his son.”

Lai is allowed two 30-minute visits by relatives or friends each month. They are separated by glass and communicate by phone.

In a separate case, he was sentenced in December to almost six years in prison on fraud charges.

In May, a court rejected Lai’s bid to halt his security trial on grounds that it was being heard by judges picked by Hong Kong’s leader. That is a departure from the common law tradition China promised to preserve for 50 years after the former British colony returned to China in 1997.

Lai, who suffers from diabetes and was diagnosed with high blood pressure in 2021 while in detention, is treated as a Category A prisoner, a status for inmates who have committed the most serious crimes such as murder.