In 2010, nearly 80,000 Americans were denied guns after providing false information about their criminal histories during the background check. Technically, it's a felony to lie during this process. Yet only 44 would-be buyers were ever charged with a crime, according to the New York Times.

That may sound like a weirdly obscure statistic. But it's a statistic that has become increasingly central to the debate over guns inside Congress.

Gun-control advocates are currently pushing for Congress to expand the system of background checks so that it covers all gun sales — not just sales at federally licensed gun dealers, but also private sales between individuals or at gun shows. Groups like the National Rifle Association (NRA), by contrast, say these expanded laws are likely to be ineffective so long as the government doesn't even prosecute existing violations.

This question flared up yet again during a hearing on assault weapons in the Senate Judiciary Committee on Wednesday. Sen. Lindsay Graham (R-S.C.) was asking John Walsh, the U.S. Attorney for the District of Colorado, why the Obama administration pursues so few cases against people who lie on their background checks.

"How many prosecutions," Graham asked, "have you taken up for failing a background check since you've been U.S. Attorney?"

"Off the top of my head, I'm not aware of any," Walsh said.

Graham was visibly angry at that answer. "What kind of deterrent is that? The law is obviously not seen as that important. Why aren’t we prosecuting people who fail a background check?"

But there was an explanation, or at least an attempt at one. After a heated back and forth, Milwaukee Police Chief  Edward A. Flynn argued that these specific types of prosecutions were largely a distraction. "It's a paper thing. I want to stop the 76,000 people who are buying guns illegally," he said. "If you think we're going to do paperwork prosecutions, we're wrong."

In a later exchange with Sen. John Cornyn (R-Tex.), Walsh agreed, arguing that there was little point in going after people who had already failed background checks — since they were unable to buy guns anyway. "There's no way the Department of Justice could have prosecuted all 1.5 million people who were rejected over that 15 year period."

In the past, Justice Department officials have also said that these crimes are inherently difficult to prosecute, because it's tough to prove that someone was knowingly and deliberately lying on his or her form.

It's worth noting, though, that some gun-control advocates do seem to side with Graham in this narrow case. The group Mayors Against Illegal Guns, for instance, has argued that the federal government should do more to investigate those denied guns because of their criminal background. A 2008 study by the Justice Department found that people denied guns in this way were 28 percent more likely to commit a crime in the next five years.

Yet gun-control groups also add that these investigations should come alongside new laws for universal background checks — rather than acting as a substitute.

Further reading:

--Obama wants universal background checks for gun buyers. Is that feasible?

--Here's the latest on the congressional debate over universal background checks. It's being held up by a disagreement about record-keeping.