Domestic violence are repeated incidents of abuse (including physical and economic ones) on a victim such as a spouse in a domestic context. The abuse can be an assault occasioning actual bodily harm (AOABH), and may couple with a threat to pay money, or further harm will follow. Such AOABH and blackmail are crimes committed at home.
For AOABH, the assault must cause actual bodily harm which needs not be serious or permanent. The maximum penalty in Hong Kong is 3-year imprisonment under s.39 of the of the Offences Against the Person Ord, Cap 212. Upon conviction, the actual sentence would depend on the facts of each case and the circumstances of the accused.
For blackmail, the unwarranted demand made must be intended to gain for one or cause loss to another. The menace is unwarranted if a person has no reasonable grounds for making the demand and the use of menace is not a proper means of reinforcing it. The maximum penalty is 14-year imprisonment under s.23 of the Theft Ord, Cap 210.
The Department of Justice of Hong Kong has a prosecution policy on cases involving domestic violence. Public interest normally requires prosecution, if the victim is willing to testify. I have come across a reluctant prosecution witness who wanted to preserve the family, and a willing one who wanted to end the relationship!