One of the few tycoons who dared to insult the Chinese Communist Party, Jimmy Lai has long been a thorn in Beijing’s side. With his popular Chinese-language newspaper, Apple Daily, he backed pro-democracy protests that swept over Hong Kong in 2019.

Mr. Lai, 77, was one of the first and most prominent targets of a national security law that Beijing imposed on Hong Kong the following year, under which more than 340 people have since been arrested.

He has been behind bars since December 2020, and is also serving a five-year sentence for fraud after being convicted of violating the terms of a lease agreement. In 2021, he was sentenced to one year in prison, along with other pro-democracy figures, over his role in an unauthorized peaceful protest. His health has faltered after years in detention.

His latest trial, on the most serious charges against him, is now coming to an end.

Here’s what to know.

Who is Jimmy Lai?

Mr. Lai is a self-made businessman who made his fortune in textiles. Born in China in 1947, he stowed away on a boat to the then-British colony of Hong Kong at age 12 and worked his way up the factory floor. He founded Giordano, a clothing chain with stores across Asia. He later acquired British citizenship.

He was a rare tycoon who did not keep quiet about his political stance.

When student activists in China protested for a more democratic government in 1989, he printed T-shirts with the faces of activists. After Chinese troops killed hundreds, possibly thousands, of demonstrators who had occupied Tiananmen Square in Beijing, Mr. Lai decided to become a publisher, launching Next Magazine in 1990 and Apple Daily in 1995.