In Canada the rule of thumb for self defense is that you don't use anything that someone else hasn't already brought to the party; up to and including grievous bodily harm or death. (Sections 34-37)
(Example, if someone grabs your arm in a threatening manner (assault), you can use moderate force to dislodge them; not dislodge them in a manner that dislocates their elbow, pops their eardrum, shatters their knee and then takes their teeth out one by one on the curb.)
So if in course of the home invasion, if the suspect, through threat/action/armament placed you in fear for your life, a lethal response can be justified. You have to be able to stand tall in front of the judge and justify your use of force.
(Example, if someone grabs your arm in a threatening manner (assault), you can use moderate force to dislodge them; not dislodge them in a manner that dislocates their elbow, pops their eardrum, shatters their knee and then takes their teeth out one by one on the curb.)
So if in course of the home invasion, if the suspect, through threat/action/armament placed you in fear for your life, a lethal response can be justified. You have to be able to stand tall in front of the judge and justify your use of force.