Sixteen Hong Kong pro-democracy figures face trial on Monday, more than two years after their arrest, in what some observers say is a landmark case for the city's judicial independence under a national security law imposed by Beijing.

The defendants are those who pleaded not guilty out of 47 arrested in a dawn raid in January 2021 and charged with conspiracy to commit subversion for participating in an unofficial primary election in 2020.

Thirteen of those arrested were granted bail in 2021, while the other 34 — including 10 who pleaded not guilty — have been in pretrial custody on national security grounds.