"Castle laws" are a broad, generic term for laws that assign a "special" consideration for actions taken in your home and/or business in response to crimes. Hawaii's Castle laws are relatively weak. While they allow you the option of not retreating from a threat in your home, it does not assign a presumption that the criminal who broke in is there with intent sufficient to justify the use of deadly force. Neither does it provide any protection from any subsequent civil actions brought forth by either the criminal or his survivors.
So, while you may not need to retreat from your home during a home invasion, in order to legally justify the use of deadly force you would have to be able to articulate the fear of death, great bodily injury, kidnapping, rape or forcible sodomy: the same justification as if you were out of your house. Many of the other states "castle laws" include a provision that if someone is in your home illegally, or entered by force, they are PRESUMED to be there with intent sufficient to warrant a response of deadly force by the homeowner/occupant. Many of them also have an exemption from civil liability.
These are some of the features of the "castle law" HRA tried to get passed last year......