If you are looking for a round that is lethal, yet will NOT penetrate through walls in your home, look at the Glaser round, which is what I use in home and public defense. It does NOT ricochet, and will stop at the point of contact, so no going through walls. you can find it at pretty much ANY ammunition retailer. I will agree with most here in saying that the safest gun is...NONE. There are no SAFE guns. Every gun is potentially lethal in the hands of a human being. so ALWAYS treat a firearm as loaded at ALL times. You had mentioned that you didn't intend on getting a CCW permit, but I would HIGHLY suggest you and your wife taking a CCW permit class, jsut for the GREAT knowledge that you will get from it. Many firearm safety classes teach you the basics on HOW to use a firearm, and HOW to clean it and keep it safe. Your local CCW class will teach you WHEN to use it (specifics in legal standpoint for your state, since the CCW is a STATE level license) and THAT is your best knowledge. I always have said and always will say that the best time to fire at your target(i.e. intruder) is when you KNOW who it is. ALWAYS identify your target BEFORE firing PERIOD! don't EVER fire through a door or fire blind. too many people have killed family members simply because they paniced and failed to identify WHO they were shooting. I have NEVER fired my pistol without knowing what it was pointed at, and what was a potential hazzard AROUND my target. It only takes a fraction of a second to identify your target, but it takes YEARS, if ever, to get over killing a member of your family on accident! I am honestly supprised after all the dicussion of various handguns here, and yet NOBODY has mentioned my favorate one, the Springfield Armories xd40, or xd45 ACP. It is a WONDERFUL handgun with trigger, handguard, and firing pin safeties. All of which are unlocked simply by griping the handgun properly. no need to flick a lever, or do anything. Just grab it and fire. It has a zero percent chance of accidental discharge when dropped or struck. Check it out here if you have never seen it. this is the one that I have....
SA XD-40 subcompact