A spring gun is the classic case of "defending PROPERTY" as opposed to self-defense -- because using the spring gun means you're not even at the scene, so clearly no self-defense attaches.
I raised the hypo because the writers on this thread are SAYING that its OK to use lethal force to defend PROPERTY, and then the illustrations offered are NOT clearly defense of property, but variations of self-defense.
So I want to put the question clearly on the table -- is it OK to use a spring gun as I hypothesized? If you say NO, then you are agreeing that defense of PROPERTY does not warrant lethal force.
Even the statutes are muddy -- in the Texas statute, for example, "robbery" requires that a PERSON is robbed -- it's an element of the crime. And I suspect that a careful reading of the statute points to self-defense, not defense of property, although the title states otherwise.
I've had the experience of defending in a murder trial where self-defense was asserted by my client -- dso I speak from some experience here.