No one really wants to answer your question. Most likely because you seem to either be considering burglarizing some poor woman's house for cookies and wondering if you will be shot or are considering shooting someone in your own house. I highly advise against either scenario, but the short answer is: Washington allows the "castle exception." Google it.
Reasonable force depends on the fact situation for example if a grown man comes into your house with a knife and comes to close shoot the bastard. But if a ten year old is trying to steal a bicycle out of your backyard do not shoot, I can not give you much more help as the fact pattern really depends on the amount of present or perceived danger
My name is Stephen R. Cohen and I have practiced over 38 years and can be reached at 213-819-1171. I practiced mainly in Los Angeles and Orange County, California. I am not seeking clients from existing relationships with other attorneys, and give only limited advise over the phone (the phone is primarily used to set appointments), these services do not create an attorney client relationship. I apologize for mispelling< as I am a lousy typist, My answers may offend as I do not believe in pulling punches or sugar coating the truth. Further regarding courts in other states my opinions are largely based on logic and what I think is the modern trend which is to consider the needs of the child.
A resident has the right to defend himself or herself and property, but if a resident shoots and injures or kills an intruder, the police might just charge the resident with assault, manslaughter, or murder. The resident's beliefs or opinions about use of force are not going to be a factor in the police or prosecutor's decision on whether to charge, and there is no way to provide a guideline for whether a particular use of force is justified: it is always a decision that is going to be made after the fact. Fair or not, that is how it works.
There is no duty to retreat prior to using force in Washington, but any use of force must be reasonable under the circumstances. The prosecutors are the people who make the decision whether to charge, and ultimately the jury would decide what is "reasonable."
Some simple (intentionally vague) rules to live by are 1) Don't shoot if you don't have to; and 2) do not unlawfully enter another person's home, because you might get unlawfully shot.
A burglar is very unlikely to succeed in a lawsuit against a homeowner who shot him or her, but it is certainly possible if the facts are very compelling. Your example about the cookies and crazy homeowner is not very compelling.
Also, generally, most people who are being burglarized are going to believe that their life is in danger, so the fact that a person is hiding in the attic just reinforces the determination that the person believed that her life was in danger. The police and prosecutors are likely to agree. If the burglar has left the home and gets shot by the homeowner while fleeing, then that is a completely different situation.
Reasonable force to defend yourself, family and property is the standand. These matters are very fact specific and there is no way to PRE determine the correct responce to a given set of facts because there are too many variables. If something happens then consult an experienced criminal defense attorney.