No intention of hijacking this thread, though here's some food for thought on the matter in general. (Don't shoot the messenger here, these are simply thoughts from a discussion)
Having years of law enforcement in my past, as well as a family member who before retirement, served as an assistant DA, we've discussed, hypotheticly, some of the scenerios posed here.
His concensus is that, (based on) individual responses here, as well as some posted photos, He would more than likely pursue criminal charges against the home defender, even though, they did in fact believe they were defending life and property.
The reason being, there was obviously premeditation about self defense, ammunition used with the intent of inflicting the most damage or death, as well as the design of a "specialty" weapon for this exact purpose.
As he puts it, there is a distinct difference between protecting ones home with grandpa's old (shotgun of choice) should a break in occur, the planning and practice some people practice. Therefore its a fine line between being prepared and being seen as an aggressor, and as he puts it, he could easily convince a jury that the shooter had in fact been planning for such an occasion and was looking forward to the opportunity to stop by any means, such an attack.
We also discussed what might be a reasonable (legally speaking) home defense shotgun and ammo, and agreed that the following would provide plenty of plausible deniability.
a midrange priced pump or autoloader, with a shorter 26 inch bbl and screw in chokes, using an improved cylinder tube. For ammo factory or handloaded 1 1/4 to 1 1/2 ounce of lead BB or BBB shot at nominal hunting velocities. (Since these loads could in fact be readily available as turkey loads it could be argued they were not designed primarily for self defense.)
The argument by a defense lawyer would of course be, that it was a shotgun designed for hunting as was the ammo thus at least while used as home protection that wasnt the prime goal.
Now these thoughts are from a couple of pro gun folks, just imagine what the anti gunners could do with it in court?