I would imagine direct theft (by the criminal), indirect theft (criminal buying from a fence), and known unlawful sales (unscrupulous pawn shop guy, or a friend of the criminal, sells to the criminal) far outweigh guns obtained from law-abiding citizens.
Whoa there, let's go back to the topic at hand here. It was, essentially that we should lock our guns up as much as we can when we aren't using/carrying them. The logic being that it will help prevent theft (houses are easy to break into, safes not as much).
When I said that criminals get their guns from law abiding citizens, this is what I was referring to.
Direct Theft - Who are they stealing from? Law abiding citizens.
Indirect Theft - Where did the fence get the gun? A criminal. Where did that criminal get the gun? Most likely (certainly, not always) from a theft (if they're using a fence to off load hot items) of a law abiding citizen.
Unlawful Sales - This is the only one of the 3 you mentioned where they aren't getting the guns, necessarily from a law abiding citizen. And in some cases, they still are (good guy sells to a bad guy, for example).
The point I was trying to hammer home was that if you want to help keep guns out of criminals hands, making sure your guns are locked up and secured, besides being behind a locked front door, will make a great first step.
That's all I meant. Nothing about NFA. Nothing about cartels, and drug lords. Just about where armed criminals most likely get guns from...they originate from a law abiding citizen, who knowing he's protected from legal liability by keeping his guns behind a locked front door, doesn't secure his guns, and then he has a break in and they get stolen. There's no way to substantiate this since most gun thefts don't get reported (I've heard anywhere between only 10% to 30% are actually reported).
Guns in criminals hands have to come from somewhere. Assuming that NICS is 100% (I know it's not, but the false negative rate of NICS can't be substantiated either), a criminal can't buy one, he'll get a NICS rejection. As you said, those are the only three options, and most guns within those three options come from theft of a law abiding citizen.
The Border Patrol also has a bean bag loaded as the first round in their shotguns; this is because the Border Patrol does what Janet Napolitano and the administration tell them to do whether or not it makes sense.
I agree with your sentiment here, but this is an Ad Hoc Ergo Propter Hoc fallacy. Just because Big Sister says load your first round as a bean bag, does not mean everything the Border Patrol does is bad. But I agree, I don't completely trust what they are doing either.