Perhaps the most important moment so far in today’s Senate Judiciary hearing on guns came when astronaut Mark Kelly directly confronted NRA head Wayne LaPierre over the shooting of his wife, Gabrielle Giffords. Between that exchange and another one involving Senator Dick Durbin, LaPierre’s argument was completely unmasked for the sham that it is.

During the hearing, LaPierre repeatedly voiced the talking point that there’s no need to expand the background check system because criminals don’t cooperate with background checks. Kelly responded:

The Tucson shooter was an admitted drug user. He was rejected from the U.S. Army because of his drug use. He was clearly mentally ill. And when he purchased that gun in November, his plan was to assassinate my wife and commit mass murder at that Safeway in Tucson. He was a criminal. Because of his drug use, and because of what he was planning on doing. But because of these gaps in the mental health system, in this case, those 121,000 records, I admit did not include a record on him. But it could have.

And if it did, he would have failed that background check. He would have likely gone to a gun show, or a private seller, and avoided that background check. But if we close that gun show loophole, if we require private sellers to complete a background check, and we get those 121,000 records and others into the systems, we will prevent gun crime. That is an absolute truth. It would have happened in Tucson. My wife would not have been sitting here today if we had stronger background checks.

There are two policy conundrums here. One is this: How do you ensure that people like the Tucson shooter are represented in the national database designed to prevent criminals and the mentally ill from getting guns? There are significant gaps in this database for a variety of reasons, including the failure of states to share info with the feds. Some of Obama’s proposals are designed to fix these problems, by encouraging states to share data, reviewing data collection procedures, and so on. The second question is: How do you expand the background check system so it screens more gun sales than it currently does? The Obama proposal would do this by closing the loophole that allows guns to be sold without background checks at gun shows and by private sellers. As Kelly notes, the likelihood is that someone like the Tucson shooter — even if he were denied guns by the currently functional part of the background check system — would then try to get guns via a private seller. Closing the loophole could block that.

There is no evidence for LaPierre’s suggestion that background checks don’t work. Indeed, as my Post colleague Glenn Kessler has shown, in 2010 alone tens of thousands of people with felony and criminal backgrounds were denied guns by checks. More broadly, over 1.5 million gun sales to people who are prohibited from having guns have been blocked by background checks. There is no way to know what would have been done with those guns had those sales gone through, since that is a counter-factual. But the question for those who oppose background checks remains a simple one: Do you think we would be better off if those sales had gone through, or is it a good thing that those sales were blocked?

And LaPierre’s suggestion fails the test of basic logic. If criminals don’t cooperate with background checks, and end up getting their guns from private sellers or gun shows, or from gun dealers who get them via such means, that is an argument for expanding the background check system, not an argument against it. Indeed, these loopholes are the very reason that gun crime persists even in areas that have strict gun control. The “gun rights” crowd likes to point to Chicago as an example of such a place. But as Senator Dick Durbin put it during the hearing:

When you take a look at where these guns come from, 25 percent plus are sold in the surrounding towns around the city of Chicago, not in the city. Look over the last 10 or 12 years. Of the 50,000 guns confiscated in crimes, almost one out of 10 crime guns in Chicago came to that city from Mississippi. Why? Because the background checks there, the gun dealers there, are a lot easier than in other places. And they end up selling these guns in volume.

At the hearing, Maryland police chief Jim Johnson, who is also the Chair of the National Law Enforcement Partnership to Prevent Gun Violence, echoed the arguments of Kelly and Durbin almost to the letter, and said the law enforcement officials in his organization agree. So on background checks right now, here’s the score: It’s the NRA, the gun industry, and leading GOP (and a few red state Dem) officials on one side, and the nation’s law enforcement officials and the vast majority of the American public, Republicans, NRA households and gun owners included, on the other.