Defensive gun use

Estimates over the number of defensive gun uses vary.

Defensive gun use (DGU) is the use of a firearm in self-defense or defense of others. The frequency of defensive firearms incidents, and their effectiveness in providing safety and reducing crime is a controversial issue in gun politics and criminology. Different authors and studies employ different criteria for what constitutes a defensive gun use which leads to controversy in comparing statistical results. Perceptions of the number of DGUs dominate discussions over gun rights, gun control, and concealed carry laws.

Estimates of frequency

Estimates over the number of defensive gun uses vary wildly. Ranging between a high end of 33 Million incidents per year and a low end of 127 incidents per year, depending on the study's definition of a defensive gun use, survey design, population, criteria, time-period studied, and other factors. The higher end survey estimating between 12.9 and 33.1 Million annual defensive gun uses comes from a 1994 telephone survey titled The National Survey of Private Ownership of Firearms performed by the firm Chilton Research Services . A commonly cited estimate by Kleck and Gertz shows between 1 to 2.5 million DGUs in the United States each year. Another estimate has estimated approximately 1 million DGU incidents in the United States. Lower end estimates include that by David Hemenway, a professor of Health Policy at the Harvard School of Public Health, show approximately 55,000-80,000 such uses each year. At the low end, a recent study of data from the National Crime Victimization Survey (NCVS) identified only 127 self defensive gun uses per year.

The National Self-Defense Survey and the National Crime Victimization Survey (NCVS), vary in their methods, time-frames covered, and questions asked. DGU questions were asked of all the NSDS sample. Due to screening questions in the NCVS survey, only a minority of the NCVS sample were asked a DGU question. Estimates of DGU from the NCVS are consistently lower than those from other studies. A 2000 study suggested that this may be because the NCVS measures different activities than the other surveys do. Besides the NSDS and NCVS surveys, ten national and three state surveys summarized by Kleck and Gertz gave 764 thousand to 3.6 million DGU per year. Hemenway contends the Kleck and Gertz study is unreliable and no conclusions can be drawn from it. He argues that there are too many "false positives" in the surveys, and finds the NCVS figures more reliable, yielding estimates of around 100,000 defensive gun uses per year. Applying different adjustments, other social scientists suggest that between 250,000 and 370,000 incidences per year.

Another survey including DGU questions was the National Survey on Private Ownership and Use of Firearms, NSPOF, conducted in 1994 by the Chiltons polling firm for the Police Foundation on a research grant from the National Institute of Justice. NSPOF projected 4.7 million DGU per year by 1.5 million individuals after weighting to eliminate false positives. Discussion over the number and nature of DGU and the implications to gun control policy came to a head in the late 1990s.

A study published in 2013 by the Violence Policy Center, using five years of nationwide statistics (2007-2011) compiled by the federal Bureau of Justice has found that defensive gun uses (DGU) occur at a dramatically lower magnitude than that suggested by Kleck: an average of 67,740 times per year.

In the report "Guns in America: National Survey on Private Ownership and Use of Firearms" by Philip J. Cook and Jens Ludwig, the authors quote the National Crime Victim Survey (NCVS) as finding 108,000 DGU per year. The gun use survey included in the NSPOF itself projected 4.7 million DGU which Cook and Ludwig explained by pointing out all of the NSPOF sample were asked the DGU question. Cook and Ludwig also compared the U.S. crime rate to the number of DGU reported by Kleck and similar studies and said that their estimate of DGU is improbably high. A 1994 study examined NCVS data and concluded that between 1987 and 1990, there were approximately 258,460 incidents in which firearms were used defensively in the United States. The same study said that "Firearm self-defense is rare compared with gun crimes."

An article published by the Bureau of Justice Statistics, drawing its DGU from the NCVS, said: "In 1992 offenders armed with handguns committed a record 931,000 violent crimes ... On average in 1987-92 about 83,000 crime victims per year used a firearm to defend themselves or their property. Three-fourths of the victims who used a firearm for defense did so during a violent crime; a fourth, during a theft, household burglary, or motor vehicle theft." Cook and Ludwig said of the NCVS, NSPOF, and Kleck surveys: "The key explanation for the difference between the 108,000 NCVS estimate for the annual number of defensive gun uses and the several million from the surveys discussed earlier is that NCVS avoids the false-positive problem by limiting defensive gun use questions to persons who first reported that they were crime victims. Most NCVS respondents never have a chance to answer the defensive gun use question, falsely or otherwise."

Clayton Cramer and David Barnett say that such a structure could cause the NCVS to under-count defensive gun uses, because someone who has successfully defended themselves with a gun may not consider themselves a "victim of a crime." In the NCVS, if one says that they have not been a victim of a crime, the survey assumes that there was no attempted crime and does not go on to ask if they have used a gun in self-defense.

Kleck gives another explanation of the discrepancy, which is that the NCVS estimate is too low because it never asks a respondent about defensive gun use. (He says that it asked a generic, open-ended question about anything that the victim might have done for self-protection.) Kleck says that many other surveys (at least 20) have likewise obtained huge estimates of DGU frequency, from 500,000 to over 3 million per year -common enough to outnumber criminal uses and further notes that studies of methodological errors in surveys concerning other crime-related behaviors and experiences have consistently found that the errors produce, on net, underestimates of the frequency of the behaviors, including victimization experiences, offending behavior, and gun ownership. He has said that critics' assessment of possible errors in surveys are one-sided - that they consider only flaws that would contribute to overestimation of defensive gun use frequency. Kleck says that critics fail to take into account of flaws that would contribute to an underestimation of defensive gun uses, such as a tendency of survey respondents to conceal or otherwise fail to report controversial acts they have committed, victimization experiences, and gun ownership. He says that it is logically impossible to determine whether surveys overestimate or underestimate the prevalence of such experiences if one does not establish the relative balance of the two kinds of error.

Kleck asserts errors in his critics' statements that his survey's estimates of defensive gun uses linked with specific crime types, or that involved a wounding of the offender, are implausibly large compared to estimates of the total numbers of such crimes. The total number of nonfatal gunshot woundings, whether medically treated or not, is unknown, and no meaningful estimates can be derived from his survey regarding defensive gun uses linked with specific crime types, or that involved wounding the offender, because the sample sizes are too small. The fact that some crime-specific estimates derived from the Kleck survey are implausibly large is at least partly a reflection of the small samples on which they are based - no more than 196 cases. Kleck states that his estimate of total defensive gun uses was based on nearly 5,000 cases. Thus, he argues, the implausible character of some estimates of small subsets of defensive gun uses is not a valid criticism of whether estimates of the total number of defensive gun uses are implausible or too high.

Criminologist Marvin Wolfgang, who described himself "as strong a gun-control advocate as can be found among the criminologists in this country" and whose opinion of guns was "I would eliminate all guns from the civilian population and maybe even from the police. I hate guns--ugly, nasty instruments designed to kill people" defended Kleck's methodology, saying "What troubles me is the article by Gary Kleck and Marc Gertz. The reason I am troubled is that they have provided an almost clear-cut case of methodologically sound research in support of something I have theoretically opposed for years, namely, the use of a gun in defense against a criminal perpetrator". He went on to say that the NCVS survey did not contradict the Kleck study and that "I do not like their conclusions that having a gun can be useful, but I cannot fault their methodology. They have tried earnestly to meet all objections in advance and have done exceedingly well."

However, both Kleck and Gertz' and Lott's research have come under considerable fire from the academic community. Critics such as Hemenway have pointed to the fact that their study ignores problems that arise from telescoping, the social desirability bias, and strategic responses by gun rights advocates, all of which can lead to significant false positives. In addition, a 2004 study surveyed the records of a Phoenix, Arizona newspaper, as well as police and court records, and found a total of 3 instances of defensive gun use over a 3.5 month period. In contrast, Kleck and Gertz's study would predict that the police should have noticed more than 98 DGU killings or woundings and 236 DGU firings at adversaries during this time.

Hemenway research

In 2000, Hemenway published a survey which found that "Guns are used to threaten and intimidate far more often than they are used in self defense"; also that year, he published another survey which found that "criminal gun use is far more common than self-defense gun use." Both of these surveys argued that many defensive gun uses may not be in the best interests of society. A later survey by Hemenway et al. that included 5,800 California adolescents found that about 0.3% of these adolescents reported having used a gun in self-defense.

Lott research

Researcher John Lott argues in both More Guns, Less Crime and The Bias Against Guns that media coverage of defensive gun use is rare, noting that in general, only shootings ending in fatalities are discussed in news stories. In More Guns, Less Crime, Lott writes that "[s]ince in many defensive cases a handgun is simply brandished, and no one is harmed, many defensive uses are never even reported to the police".

Attempting to quantify this phenomenon, in the first edition of the book, published in May 1998, Lott wrote that "national surveys" suggested that "98 percent of the time that people use guns defensively, they merely have to brandish a weapon to break off an attack." The higher the rate of defensive gun uses that do not end in the attacker being killed or wounded, the easier it is to explain why defensive gun uses are not covered by the media without reference to media bias. Lott cited the figure frequently in the media, including publications like the Wall Street Journal and the Los Angeles Times.

In 2002, he repeated the survey, and reported that brandishing a weapon was sufficient to stop an attack 95% of the time. Other researchers criticized his methodology, saying that his sample size of 1,015 respondents was too small for the study to be accurate and that the majority of similar studies suggest a value between 70 and 80 percent brandishment-only. Gary Kleck and Marc Gertz's 1994 estimate rises to 92 percent when brandishing and warning shots are added together. Lott explained the lower brandishment-only rates found by others was at least in part due to the different questions that were asked. Most surveys used a recall period of "Ever" while some (Hart, Mauser, and Tarrance) used the previous five years. The Field Institute survey used periods of previous year, previous two years and ever. The NSPOF survey used a one-year recall period. Lott also used a one-year recall period and asked respondents about personal experiences only, due to questionable respondent recall of events past one year and respondent knowledge of DGU experiences of other household members.

See also

• Castle doctrine
• Justifiable homicide
• Stand-your-ground law