Myth: A gun in the home increases personal safety.



Fact: A gun in the home make homicide 2.7 times more likely.







Summary



Keeping a gun in the home carries a murder risk 2.7 times greater than not keeping one, according to a study by Arthur Kellermann. The National Rifle Association has fiercely attacked this study, but it remains valid despite its criticisms. The study found that people are 21 times more likely to be killed by someone they know than a stranger breaking into the house. Half of the murders were over arguments or romantic triangles. The study also found that the increased murder rate in gun-owning households was entirely due to an increase in gun homicides only, not any other murder method. It further found that gun-owning households saw an increased murder risk by family or intimate acquaintances, not by strangers or non-intimate acquaintances. The most straightforward explanation is that the presence of a gun increases the possibility that a normal family fight or drinking binge will become deadly. No other explanation fits the above facts.







Argument



Most people keep guns in their homes for self-protection. The image of an unknown criminal breaking into your house is an important one for gun advocates, because it justifies keeping a gun in the home. But to gun control advocates, a gun in the home means that a family fight or a drinking binge is more likely to turn deadly. Which view is more accurate?



In an attempt to answer this question, a team led by Dr. Arthur Kellermann of Emory University conducted a survey of 388 homes that had experienced homicides. (1) They found that 76.7 percent of the victims were killed by a spouse, family member or someone they knew, and there was no forced entry into the home 84.3 percent of the time. Strangers comprised only 3.6 percent of the killers. However, the killer was never identified in 17.4 percent of the cases.



Of the 420 homicides they originally investigated, 96.4 percent were illegal. Only 3.6 percent were ruled legally excusable homicide (that is, self-defense).



After eliminating the impact of other variables like illegal drugs and domestic violence, the researchers found that the risk of getting killed was 2.7 times greater in homes with a gun than without them. No protective benefit of possessing a firearm was ever found, not even for a single one of the 14 subgroups studied.



Needless to say, the National Rifle Association and other pro-gun advocates have fiercely attacked this survey. Kellermann's work has been branded "junk science," "unpublishable," "biased," "seriously flawed," "fraudulent" and "grand malpractice." The NRA also criticized the Centers for Disease Control for continuing to fund such anti-gun research, and the Republican Congress pressured the CDC to shut it down completely. Thus, the reaction of Republicans and the NRA to this controversial study was not to call for more studies to clarify the issue, but to censor all further scientific research.



Pro-gun advocates respond that they are not promoting censorship, only objecting to wasting tax dollars on blatantly biased, deeply flawed research. Pro-gunners feel that the sound bites generated by this study will become part of a popular mythology against guns that will be hard to correct. But this objection is based on a faulty view of the research method. The best way to correct bad science is to subject it to expert criticism: namely, peer review. Kellermann's study was, and it passed. Pro-gunners might then wish to criticize the peer review process. For example, they might accuse Kellermann's peer reviewers of sharing his bias (although there are protocols in peer review to avoid this). The principled response, then, would be to examine and reform the peer review process. For example, Republicans in Congress might have called for pro-gun criminologists like Gary Kleck to be included in all future peer review of CDC-funded studies. Another principled response would be for the NRA -- one of the richest organizations in America -- to start funding its own research by way of rebuttal. But to shut down all further research is both censorship and anti-science.



It is apparent from the attacks on Kellermann's study that most of his critics have not even read it. Simply reading the original article in The New England Journal of Medicine (October 7, 1993) would answer 95 percent of their objections. The study was well-designed and is entirely valid. Like any scientific study, it has its limitations. It does not prove that guns cause a higher murder rate in the home, only that the two are associated for some reason. And there are more variables that need to be explored. But the Kellermann study is a legitimate addition to the small but growing scientific literature on the benefits and costs of domestic firearms.



The rest of this essay will be divided into two parts: a detailed description of the Kellermann survey, and a rebuttal of its criticisms.



The survey



Kellermann chose to conduct this survey using the "case-control method" (or CCM). This method examines the differences between two groups: one that possesses a certain trait, and another that does not. For instance, a researcher may compare a "case group" that has lung cancer to a "control group" that is free of the disease. After asking them questions about their behavior and environment, he may learn that the case group generally smokes, but the control group does not. Conclusion: smoking is correlated to lung cancer. In this instance, the arrow of causality is easy to determine, because it is unlikely that lung cancer causes people to start smoking. But sometimes the arrow of causality is more difficult to determine, as in the case of gun ownership and murder.



Kellermann's team identified 388 victims ("case subjects") who were killed in private homes. Surviving members of the household ("proxies") formed the case group which answered the survey. The researchers also gave an identical survey to a control group of 388 other people, who were matched to the victims by age, race, sex and neighborhood.



The homicides which were studied came from three metropolitan areas. The first two were Shelby County, Tennessee (which includes Memphis), and King County, Washington (which includes Seattle), both from August 1987 to August 1992. The third was Cuyahoga County, Ohio (which includes Cleveland), from January 1990 to August 1992. King County is predominately white and enjoys a relatively high standard of living. Cuyahoga County is 25 percent African-American, as is 44 percent of Shelby County. The poverty levels of these counties were 5, 11 and 15 percent, respectively. (The national poverty rate in 1992 was 15 percent.)



The team originally identified 444 cases of homicide in the home, about a fourth of the total number of homicides for those counties. This number was reduced to 420 for the study for various reasons, then to 405 because a control couldn't be found, and then to 388 because a proxy couldn't be interviewed. The high response rate of case proxies (92.6 percent) and matching controls (80.6 percent) is typically considered to have minimized nonresponse bias.



The survey asked 31 questions about the subjects' environment and behavior. The results are listed below. The first two columns reflect the percentage of those who answered yes to the question. The third column reflects the crude odds that a murder would be more likely for those who answered yes. For example, for the first question, murder was 2.4 times more likely in a household where any member drank alcohol. An odds ratio of 1.0 represents no extra risk. Keep in mind that the crude odds are confounded by other variables, and by themselves do not tell the whole story. Another analytical step is needed to arrive closer to the truth.

Case Control Crude odds Behavioral factors Subjects Subjects Ratio --------------------------------------------------------- Any household member drank 73.3% 55.9% 2.4 alcoholic beverages Case subject or control drank 62.8 41.9 2.6 alcoholic beverages Drinking caused problems 24.8 5.7 7.0 in the household Any household member had 9.0 0.8 10.7 trouble at work because of drinking Case subject or control had 5.5 0.3 20.0 at work because of drinking Any household member 11.4 2.3 9.8 hospitalized because of drinking Case subject or control 7.6 0.5 14.0 hospitalized because of drinking Any household member used 31.3 6.0 9.0 illicit drugs Case subject or control 20.3 4.2 6.8 used illicit drugs Any physical fights in the 25.3 3.4 8.9 home during drinking Any household member hit or 31.8 5.7 7.9 hurt in a fight in the home Any family member required 17.3 2.1 10.2 medical attention because of a fight in the home Any adult household member 29.9 18.8 2.1 involved in a physical fight outside the home Any household member arrested 52.7 23.4 4.2 Case subject or control 36.0 15.7 3.5 arrested Environmental Factors Home Rented 70.4 47.6 5.9 Public Housing 11.1 9.8 1.5 Case subject or control 26.8 11.9 3.4 lived alone Deadbolt locks 68.8 75.3 0.8 Window bars 19.2 20.9 0.8 Metal Security Door 25.4 26.8 0.9 Burglar alarm 7.1 11.1 0.6 Controlled security access 13.9 9.8 2.3 to residence Dog or dogs in home 24.2 22.4 1.1 Gun or guns in home 45.4 35.8 1.6 Handgun 35.7 23.3 1.9 Shotgun 13.6 16.8 0.7 Rifle 12.2 13.9 0.8 Any gun kept unlocked 29.6 17.8 2.1 Any gun kept loaded 26.7 12.5 2.7 Guns kept primarily for 32.6 22.2 1.7 self-defense

The above chart is an example of "univariate analysis," or a straight comparison between the two groups. But this analysis is incomplete. There are many variables that simultaneously contribute to the odds of a person being murdered: drug use, domestic violence, criminal history, level of protection, etc. A person who answers yes to the question "Does anyone in the house use illicit drugs?" might be nine times more likely to be murdered, but that doesn't eliminate all the other variables that also contribute to the total murder risk. To isolate the risk attributed to drug use alone, researchers need to perform "multivariate analysis," which zeroes out all these other factors. That way, we can learn how drug use in and of itself raises the murder risk.



Kellermann's team found only six variables that were strong enough to be included in the final model. They found that the following variables were associated with the following increased murder risks:

Murder risk, Variable Odds adjusted ratio --------------------------------------------------- Illicit drug use 5.7 times Being a renter 4.4 Household member hit or hurt in a fight in the home 4.4 Living alone 3.7 Guns in the house 2.7 Household member arrested 2.5

If there were a protective benefit to having a gun in the home, this survey would have found it. After all, if the survey could detect an increased murder risk from the presence of a gun in the home, there's no reason it couldn't from the absence of one as well. But the team found no protective benefits of a gun in the home whatsoever, for any of the subgroups studied.



Of all the methods of murder, guns were responsible for 49.8 percent of the victims killed at home. In homes that kept a gun, the overall murder risk was 2.7 times greater, but for gun homicides it was 4.8, while for non-gun homicides it was 1.2. Notice that 1.2 is not significantly different from 1, so there was no increased risk for non-gun homicides. In other words, people who kept a gun in the home were at higher risk for gun homicides only, not any other type of homicide. This is an important point, because it strongly suggests that gun availability tends to turn ordinary family arguments into something fatal, rather than the murder victims knew they were at risk and armed themselves with a gun.



Alcohol was not included in the multivariate analysis, despite its strong association in the univariate analysis, because alcohol was also related to all the other variables in the final model. Including alcohol in the final model did not substantially alter the results. Furthermore, the odds-adjusted ratio of alcohol was not significantly greater than 1.



The researchers also conducted a stratified analysis of their final model, which found that the link between guns and homicide existed in all 14 subgroups studied. This included women as well as men, whites as well as blacks, and the old as well as the young. Most tellingly, they found the strongest association between guns and homicide among family members and intimate acquaintances (7.8 times more likely). Guns were much less associated to homicides by acquaintances, unidentified intruders, or strangers (1.8 times). Again, this supports the interpretation that guns allow family fights to turn deadly. Here is a complete list of the murder risk by subgroup:

Murder risk, Subgroup Adjusted odds ratio --------------------------------------------- Sex Female 3.6 times Male 2.3 Race White 2.7 Black 2.9 Age 15-40 3.4 Over 40 2.3 Suspect related to or intimate with victim: Yes 7.8 No 1.8 Evidence of forced entry Yes 2.5 No 2.8 Victim resisted assailant Yes 3.0 No 3.1 Method of homicide Firearm 4.8 Other 1.2

Also revealing are the circumstances surrounding the 420 homicides:

Characteristic Percent of victims --------------------------------------------------- Scene Inside residence 88.8% Within immediate property 11.2 Sex of victim Female 36.9 Male 63.1 Race or ethnic group of victim White 33.3 Black 61.9 Native American, Eskimo, Aleut 1.0 Asian or Pacific Islander 1.7 Other 2.1 Age of victim (years) 15-24 13.8 25-40 40.7 41-60 25.2 Over 61 20.2 Circumstances Altercation or quarrel 44.0 Romantic triangle 6.9 Murder-suicide 4.5 Felony-related 21.9 Drug-dealing 7.6 Homicide only 13.3 Other 1.7 Relationship of offender to victim

Spouse 16.7 Intimate acquaintance 13.8 First-degree relative 9.5 Other relative 2.9 Roommate 2.9 Friend or acquaintance 31.0 Police officer 1.0 Stranger 3.6 Unknown (unidentified suspect) 17.4 Other 1.4 Method of homicide Handgun 42.9 Rifle 2.4 Shotgun 3.6 Unknown firearm 1.0 Knife or sharp instrument 26.4 Blunt instrument 11.7 Strangulation or suffocation 6.4 Burns, smoke, scalding 2.4 Other 3.3 Victim resisted assailant Yes 43.8 No 33.3 Not noted 22.9 Evidence of forced entry Yes 14.0 No 84.3 Not noted 1.7 Legally excusable homicide Yes 3.6 No 96.4

Several points about this chart are noteworthy. The first is that at least 76.7 percent of the murderers were relatives, friends or acquaintances of the victim. In fact, the victim's murderer was 21 times more likely to be a relative or acquaintance than a stranger. Even in the 14 percent of the cases involving forced entry, the vast majority of the intruders were known to the victim. The threat of forced entry is the most commonly cited reason for possessing a domestic firearm, but the researchers found no protective benefit for this subgroup either.



The researchers write: "Efforts to increase home security have largely focused on preventing unwanted entry, but the greatest threat to the lives of household members appears to come from within."



Of the 388 homicides surveyed, 21 victims died while unsuccessfully trying to defend themselves with a gun. Only 15 of the deaths were ruled justifiable homicide or legal self-defense, and four of these were by the police.



The authors did present their study with several limitations. First, they acknowledged that they limited their study of homicides to those which occurred in the home, their goal simply being to measure the effectiveness of gun protection in the home. Homicides at other locations (such as bars, work or the streets) were not counted. Therefore, the dynamics of homicide in these locations might be quite different.



Second, they acknowledged that their research was conducted in urban settings that lacked a substantial Hispanic population. The dynamics of homicide in that community therefore might be quite different.



Third, they acknowledged that the arrow of causality could point in the opposite direction in some of the cases. For example, a person might acquire a gun in response to a specific threat. If the threat was then carried out, the correlation between the gun and the murder could be partly attributed to the failure of the weapon to provide protection.



Fourth, they acknowledged that a third, unidentified factor might be responsible for both gun possession and murder risk. For example, the victims may have had violent, aggressive personalities or some other psychological disorder that predisposed them to both greater gun possession and murder. The authors note that they included several behavioral markers for aggression and violence in their survey, but they did not conduct a full "psychological autopsy" given the impractical nature of such a task. Still, they note that "a link between gun ownership and any psychological tendency toward violence or victimization would have to be extremely strong to account for an adjusted odds ratio of 2.7."



So, what are the study's conclusions? The authors write:

"Despite the widely held belief that guns are effective for protection, our results suggest that they actually pose a substantial threat to members of the household. People who keep guns in their homes appear to be at greater risk of homicide at the hands of a family member or intimate acquaintance. We did not find evidence of a protective effect of keeping a gun in the home, even in the small subgroup of cases that involved forced entry."