The supposed allure of “ghost guns” is that they are “untraceable.” Which they are — like pretty much every other firearm in the United States. We do not maintain a national gun registry, and, in spite of what you see on television, there isn’t really any such thing as a “registered” or “unregistered” firearm as a matter of federal law and the laws of almost all the states. When police find a firearm that they believe to have been used in a crime, they can, if they choose, consult federal records that will show them which federally licensed firearms dealer sold that gun. Criminals are not as a class of people very intelligent, but even so there are not very many who: (1) are eligible to buy a gun legally from a dealer; (2) actually do so; and (3) leave that gun at the scene of a crime. But that is the only way in most cases that government records could be used to trace a gun from a crime scene to its owner. (Most cases: A couple of states maintain legally questionable databases that might provide more information.) Most firearms change hands at least once — and often several times — before they end up at a crime scene or in the hands of investigators. The thing about career criminals is — they’re career criminals. They don’t buy criminal implements from federally regulated providers. In many cases, they can’t: A large share of our murders are committed by people who already have at least one felony conviction.

Once you start looking at the statistics, you’ll notice a lot of small percentages and weak correlations — a tiny share of “assault rifles” used in murders, Hollywood-style machine guns practically nowhere in evidence, “ghost guns” more common than I would have expected (9 percent of the firearms confiscated by police in Philadelphia, for example) but still pretty rare, etc.

Where you will see much stronger correlations is in who is shooting the guns: About 90 percent of murder suspects in cities such as New York and Chicago have prior arrest histories; in Charlotte, half of the murder suspects have had prior gun charges dismissed, which is a genuine scandal; the No. 1 thing people being convicted of violent felonies have in common is a prior arrest for a violent felony, which is the case for two-thirds of violent felons.