A recent report from Violence Policy Center purports to show that private gun possession results in many more criminal firearm homicides than justified killings, a conclusion that was quickly picked up by several media outlets. But it isn’t so much a report as it is a handful of woefully incomplete data sets thrown together with a few conclusory remarks.
The essential thrust of the report is that, according to FBI homicide reporting figures, there were only 259 justified firearm homicides in 2012 compared with 8,342 criminal homicides by firearm. Ergo, the authors posit, it’s clear that private gun possession does much more harm than good, and that the claims of self-defense and Second Amendment advocates of thousands of defensive gun uses annually are wildly false.
Readers should first acquaint themselves with Brian Doherty’s excellent work over at Reason surveying the long-running debate regarding how we should conceive of defensive gun uses. Contrary to the implications of gun control advocates, the positive utility of a firearm for self-defense should not be limited to the bad guy body count:
Believe it or not, guns can and do help ensure personal safety or at least provide an insurance policy of sorts toward the time one might want or need to ensure your or your family’s personal safety even if you don’t actually plug some human varmint dead.
Certain anti-gun folk seem to sincerely believe that the only reason Second Amendment advocates want to have a gun, or want other people to have the right to have a gun, is because guns are so great at killing people; that a gun not used to kill someone isn’t really worth having. But it isn’t true.
But we have plenty of reason to believe that Americans use a gun in the service of deterring a crime or potential crime over 2 million times a year. That does not require killing someone with the gun—about three-fourths of the time the gun does not need to be fired much less kill to deter. That should be blindingly obvious to anyone not looking for some new “scientific” excuse to disarm Americans. 
Even accepting the scope of the study, there are still problems. First and foremost, the study uses unreliable data. The FBI’s Supplementary Homicide Reports, from which the number of justified homicides was tabulated by the VPC, are voluntary submissions from state and local law enforcement agencies. The vast majority of law enforcement agencies do not participate, and the data that does come in is often unreliable. For example, several instances of justified homicides were reported to the FBI as criminal homicides. 
For more than a dozen states, the FBI received no data at all on justified firearm homicides by civilians between 2008 and 2012, while only four states (Texas, California, Michigan, and Tennessee) account for nearly half (44%) of the reported justifiable gun deaths. Instead of deciding that the dearth of reliable data should breed hesitation, the authors arrive at a figure that implies there were no justified firearm homicides in non-reporting states during the study period. 
A quick glance at Cato’s map of defensive gun uses would have shown the authors several justified firearm homicides in those states.
Lastly, theVPC study makes absolutely no effort to distinguish the legality of the firearm possession that led to the homicide. Insofar as these figures are being used to advocate for additional gun control regulations, isn’t it pretty important to distinguish the guns that are illegally-owned and thus not subject to regulation in the first place? The VPC’s own website reports fewer than 200 criminal homicides by licensed firearm carriers over the entire eight year period between 2007 and 2015. That’s a far cry from 8,234 per year, and yet that data point didn’t make it into the study.
All that said, it’s important not to get lost in a statistics war over a fundamental right. As Brian Doherty notes:
The opposing armies in the [defensive gun use] war are roughly staked out with these dueling positions: 1) “There are a really large number of defensive gun uses, so many that any reasonable person would have to admit that private gun ownership is some kind of social good” and 2) “While there may be a fair number of DGUs, the number is dwarfed by the number of violent crimes committed with guns, so never mind the people who save themselves with guns, we should let politicians concentrate not on speculative and uncertain defensive uses, but on the crimes and loss of life and limb that we can see and count which accompanies gun possession and use.”
Left out of any policy decision based on these sorts of macrostatistics, as always, is how much having a gun mattered to the specific individual person able to defend himself.
However large the number of DGUs, or how small; and however large the number of accidents or tragedies caused by guns, or how small, the right and ability to choose for yourself how to defend yourself and your family—at home or away from it—remains, and that numerical debate should have no particular bearing on it.