about law ,"probono "

There is no official rule requiring a solicitor / barrister to take pro-bono cases in Hong Kong. Some solicitors / barristers would take a case on pro-bono basis out of their own free will.
The Judiciary does provide a "Duty Lawyer" service at the Magistrate Courts whereby a person can ask the Duty Lawyer to represent him in criminal cases free of charge. But in such cases the lawyer still gets paid by the government.