What kinds of cases is the doctrine of double effect supposed to explain? Do you think the doctrine offers the correct moral verdict in these cases?

The doctrine of double effect stipulates that an action is justified when the consequences of such action is not intended but occurs only a side effect of it. For instance, in the case of self-defense, an act of killing is justified if the death is only a side effect or unintended consequence but not the primary intended consequence of such one's action. The docrine offers the correct moral verdict because intentionality is key in making moral judgements. An act of self-defence is an act of preservation of life and not destroying it even if the death of another is caused in the process. This is only justified in accordance with the intention of the person who chooses to do it.