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Injury prevention class exercise: three-pronged list making
  1. David Hemenway
  1. Harvard Injury Control Research Center, Harvard TH Chan School of Public Health, Boston, Massachusetts, USA
  1. Correspondence to Professor David Hemenway, Harvard Injury Control Research Center, Harvard TH Chan School of Public Health, Boston, MA 2115, USA; hemenway{at}


It is difficult to find classroom exercises that have been specifically designed for injury prevention students. The suggested list-making classroom exercise forces students to recognise and devise many policy and programmatic options over and above the ones that normally spring to mind. Most important, it helps give students a better understanding of what is meant by, and the potential usefulness of, the public health approach to injury prevention.

  • injury
  • classroom
  • teaching
  • policy

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I have been teaching courses on injury prevention for more than three decades, and until recently, one of the few class exercises specifically designed for injury prevention was filling in examples of policies in a Haddon Matrix.1 2 The 3×3 Haddon Matrix divides prevention into human, agent (eg, product) and environmental factors, before, during and after the event. As an example, for traffic crashes agent (vehicle) characters would include good brakes that help prevent the crash, airbags that reduce injury during the crash, and good fuel type design that reduce the chance of fire immediately after the crash.

The Haddon Matrix is an incredibly useful tool for helping to illuminate the public health’s harm reduction approach. It highlights that in terms of preventive actions, there are ‘many ways to skin a cat’. The benefits for students using the Haddon Matrix is that it takes the emphasis away from looking almost exclusively at the individual behaviour of the perpetrator and/or victim just before the injury and encourages considering many other arenas for intervention. In other words, it helps students (practitioners, researchers and indeed everyone) think of many programmes and policies that might not otherwise readily come to mind. In my class, we use the Haddon Matrix to list interventions that can reduce the incidence and severity of motor vehicle injuries and firearm injuries.

I am beginning to use an additional exercise in my injury class, which I believe both complements and supplements the Haddon Matrix. This exercise forces students to recognise and devise additional policy and programmatic options over and above the ones that normally spring to mind, even after filling out a Haddon Matrix. The exercise can be used in policy classes dealing with any public health issue. I have been tentatively calling this new exercise the Three Lists.

Since I do much of my research on firearm issues, I will illustrate the tool primarily with firearm examples. In the contentious gun policy arena, too many people talk and seemingly believe that the main policy option is either taking away people’s guns or not. Like the Haddon Matrix, these three inter-related class exercises are a nice antidote to such a paucity of ideas.

What groups can help?

A hallmark of the public health approach is to try to ensure joint responsibility rather than focused blame. The first step is to get society to admit there is a problem and then to ‘roll up our sleeves’ to solve that problem. The idea is to step back and consider what can be done, and to get as many groups as possible to work together towards the common goal. A model of this approach was Sweden’s remarkable child safety initiative that began in the 1950s. This non-governmental campaign brought together many disparate groups that could affect child safety, including the Red Cross, the police, medical care providers, the automobile association, consumer groups and the media. Largely due to that initiative, between 1954 and 2000, the child injury fatality rate in Sweden fell 90%, becoming the lowest in the world.3

For the first list, the class names groups that might be enlisted to reduce the US firearm fatality rate. I suspect this is the easiest list for the students to create (I suggest warning the students ahead of time that you are going to do this exercise). This seems to be the best list to begin with, in part because there are so many potential groups—for example, firearm manufacturers, firearm retailers, firearm trainers, firearm owners, healthcare providers, hospital accreditors, the faith community, insurers, actuaries, Hollywood directors, newspaper reporters, high school teachers, hairdressers, textbook writers, advice columnists, sports heroes, standards writing organisations, financial institutions, corporations, unions, foundations, universities, students, survivors and many others. After the list is created, then consider a few specific examples about what the various groups could do. A purpose of this exercise is to emphasise that many groups can affect injury and violence directly as well as through their influence on government.

For example, here are one or two of the many actions some of these groups could take:

  1. Firearm manufacturers: manufacturers could ensure that no gun can go off when dropped, that all semiautomatics have magazine safeties to reduce accidents, and that smart guns are available that cannot be used without authorisation.4

  2. Firearm retailers: just as alcohol retailers can use best practices to reduce underage purchases, gun shops can use best practices to reduce straw purchases (buying a gun for an unauthorised person).5

  3. Firearm trainers: trainers can begin to teach about suicide prevention and as well as how to de-escalate hostile interactions.6

  4. Firearm owners: owners can store their guns in a manner to reduce firearm theft—currently some 300 000 firearms are stolen each year, a common way for guns to get into inappropriate hands.7

  5. Healthcare providers: paediatricians and other providers can ask about guns in the home and how they are stored and provide the best scientific evidence about the risk and benefits of a gun in the home.8 9

  6. Hospital accreditation: accredited trauma 1 centres currently need an injury prevention coordinator; accreditation could also require that the hospitals provide gunshot wound victims with trauma screening and crisis intervention services.10

  7. The faith community: interdenominational leaders helped immensely in the ‘Boston Miracle’, the dramatic reduction in youth homicide victimisation in the 1990s. The faith community could lead local and national efforts to reduce retaliation shootings and gun trafficking.11

  8. Insurers: insurers often provide financial incentives for safe and responsible behaviour. They could do much more in rewarding good behaviour with respect to owning and storing firearms.12

  9. Actuaries could begin collecting, analysing and disseminating information about firearm risks and benefits to insurers, andpolicymakers and the public.13

  10. Hollywood: Hollywood helps shape social norms. Thirty years ago, they played an important role in popularising the idea of the Designated Driver.14 Today, they could play a much bigger role in changing social norms concerning using violence (eg, a gun) rather than de-escalation strategies as a proper response to perceived danger.

  11. Financial institutions: Banks can stop financing makers of military style weapons for civilian use.15

  12. Academic institutions: Universities can combine their data and resources to study the effect of campus carry on fear, safety and education.16

  13. Consumers: consumers can boycott companies that engage in business practices that most endanger public safety.17

  14. Media: newspapers in cities like New York and Boston could focus less on individual shooters and victims and instead ask ‘where did the gun come from?’–investigating how it is so easy for adolescents, gang members and criminals to obtain firearms through gun trafficking.18

  15. Foundations: foundation can support street outreach in troubled neighborhoods, public education about safe storage of firearms, voter registration at gun protests, as well as data collection and research. Foundations provided the funding for the pilot of the National Violent Data System, which CDC took over and now has funding for all 50 states19; and

  16. Unions: unions can direct where their pension funds should go (eg, not to manufacturers that produce and sell bump stocks) and can educate their members to understand the dangers of allowing guns into workplaces.20

What can the government do?

When considering government action, the discussion tends to focus almost exclusively on one aspect of governmental policy—writing restrictive gun safety laws. The second exercise is for students to list generic aspects of government policy (and the various parts of government) that may be instrumental in reducing injury. I believe this will be the most eye-opening and potentially the most important of the three lists as few students will have previously recognised the vast array of governmental policy levers.

  1. Gun Regulations: everybody knows that the government passes prescriptive laws about guns that can affect firearm injury. The Giffords Law Center to Prevent Gun Violence lists scores of gun laws for each state, dividing them into nine general categories including background checks, gun sales, guns in public, crime guns, ammunition and child and consumer safety.21 Gun licensing laws, assault weapons bans and minimum age for firearm purchase are three examples of restrictive guns laws. Studies have found that stronger gun laws are associated with lower rates of gun death; there is less than compelling evidence about the effectiveness of individual laws.22

  2. Monitoring and Enforcement: Most students will recognise that government inspectors are required to monitor behaviour to determine if laws have been broken.23 Police are a type of inspector who may arrest you, but other parts of the government determine the punishment. Along with police, the criminal justice system includes prosecutors, courts and corrections (eg, prisons). Other inspectors/enforcers in the firearms area include the Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF) one of whose tasks is to oversee gun retailers. Many observers believe that the ATF’s hands have been tied in numerous ways, too often permitting retailers who do not follow the law to avoid detection or punishment.24

  3. Rewarding Good Behaviour: A less commonly used policy lever is government rewarding good behaviour. (Wouldn’t it be interesting, and newsworthy, if police randomly gave prizes for motorists making a full stop before turning right-on-red, or in Boston, yielding to pedestrians in a cross-walk?) In 2000, the government pressured Smith & Wesson to agree to help reduce crime by, among other things, requiring its authorised dealers not to sell at gun shows unless every seller at the gun show conducted background checks and providing the government with ballistics fingerprint information for all new firearms sold. What the company received in return was bad publicity from staunch gun advocates and little reward from any other source—including the government.25

    There are so many additional types of general governmental activities that affect injuries including: creating, maintaining and improving data systems; funding basic research; writing standards and testing; building and procuring; providing information and persuading and taxing/subsidising.

  4. Data systems: an initial step in the public health approach is to create good data (‘surveillance’) systems. Most students do not immediately think of data system creation as an important role for government in reducing injury. We have very good data systems for motor vehicle fatalities, which has been one reason for the major reductions in motor vehicle fatalities per mile driven over the past six decades. For many other injury areas (eg, drowning, falls), we have death certificate data but little information about circumstances. For firearms, one of my proudest accomplishments was my (admittedly limited) role in helping create the National Violent Death Reporting System. But we still do not have good information about non-fatal firearm injuries (the number, the circumstances or what eventually happens to the victims and perpetrators) or about household gun ownership and storage at the state level. And too often data that are collected are deliberately withheld from researchers.26

  5. Research funding: the ‘market’ cannot be relied on to provide sufficient basic research, on issues such as mathematics, science, cancer or heart disease, drowning prevention or violence prevention. Thus, we have the National Science Foundation, the National Institutes of Health, the Centers for Disease Control and many other agencies that provide funding for and actually perform basic research. Unfortunately, in the firearms area, there has been a deliberate attempt by powerful interests to suppress research, so we know far less than we should about what is happening and what interventions work.27

  6. Standards writing: government and non-profits, sometimes working together, write most of the product and service standards used throughout our economy.28 In many safety areas, government standards have been important in reducing injury. For example, standards for the fire-safe cigarette, now required in all states, were written by scientists at the National Institute of Standards and Technology.29 Government testing of automobile and tire safety has been critical in increasing safety competition among manufacturers. In the firearms area, standards for gun safety (eg, child proof firearms) could prove useful in reducing firearm injuries.

  7. Building and buying: government is a major builder and buyer. In the motor vehicle arena, government builds most of our roads, which can be made more or less safe. Government purchase of airbags was crucial in providing evidence for their effectiveness, allowing for their mandatory requirement.30 Many believe that if we are to have smart guns, similar to what happened with the airbag, government may have to play the role as the first main purchaser.

  8. Information and persuasion: government can both provide information and help persuade the population. The Surgeon General, for example, has a bully pulpit. The Surgeon General’s report in the 1960s on the scientific evidence linking cigarettes and cancer was instrumental in changing the dialogue and debate on that issue.31 Similarly, a Surgeon General report that summarises the overwhelming evidence linking gun access and suicide could be instrumental in changing the current discussion over gun policy.32

  9. Taxing/subsidising: taxes on cigarettes and sugar sweetened beverages have helped reduce the consumption of these commodities which have been linked to health problems like cancer and obesity. Similarly, taxes on firearms, particularly certain types of firearms such as military weapons linked with mass shootings, could help reduce our public health problems related to the misuse of firearms. Subsidies of effective gun safes could increase their use and help reduce gun theft and unintentional firearm injuries to children.

What beliefs and what social norms might be changed?

Too often discussions dealing with injury and violence prevention policy focus solely on changing government imposed mandatory requirements. For the third exercise, students list the types of social norms that could be altered to help reduce the injury problem and discuss the groups that could be enlisted in that endeavour. (This exercise should lead to an expansion of the groups listed in the first exercise.)

So that one entire class is not filled with list-making, it seems to make sense to do one exercise at the beginning of three separate classes. I suspect whatever list is done first will have the greatest impact, though if I had time for making only two lists, this would be the one I drop.

Using firearms as an example, a few of the many social norms that could be created or changed, along with incorrect beliefs that need correction, include:

  1. Selling guns to a stranger without a background check.

  2. Buying and holding guns for a boyfriend.

  3. Needing to retaliate with guns for a perceived slight or ‘dis’ (sign of disrespect).

  4. Holding the guns of friends going through a potentially suicidal period.

  5. Asking about guns if your son is going to play at a friend’s house.

  6. Firing guns in the air during celebrations.

  7. Seeing more heroism and wisdom in using a gun for protection rather than in being able to diffuse a hostile interaction.

  8. Storing firearms loaded and unlocked or hiding them.

  9. Believing that training children is sufficient to keep them safe

  10. Believing that if ‘someone wants to commit suicide, they will’.

We then talk about current and potential initiatives to change these norms and beliefs:

  1. Currently, it is legal in many states to sell a gun to a stranger without a background check. Yet even where it is legal, most people already believe it is not a proper thing to do.33 The faith community and others could step up and help ensure that virtually everyone comes to understand that selling a gun to a stranger without a background check is an immoral, reprehensible act.

  2. Most guns are bought by males, so more males than females are straw purchasers (someone who buys a gun for a prohibited purchaser). But when a woman buys a firearm she is disproportionately likely to be a straw purchaser.34 A non-profit is making headway in Boston and elsewhere working with survivors, hairdressers and others in changing social norms so that everyone (including both the woman and her boyfriend) knows what a woman should do if her boyfriend asks her to illegally purchase a gun for him—get rid of that boyfriend.35

  3. Two hundred years ago in the South, if an upper class white male was disrespected by another upper class white male, they often fought a duel with firearms. When challenged, only a coward could refuse. Many famous Americans were needlessly killed or were killers in such duels, which were unlawful. Over time, social norms changed so that challenging someone to a duel was no longer considered acceptable behaviour.36 Currently, in many urban communities, a perceived dis too often leads to gun violence. Hollywood, the faith community and others need to help change that destructive social norm.

  4. A gun in the home increases the risk of suicide threefold.37 Most suicides are fairly spontaneous, with little careful planning, and the urge passes. Keeping an at-risk individual away from deadly agents such as guns can save a life. Just as ‘friends don’t let friends drive drunk’ public health practitioners and gun advocates (including gun trainers and gun retailers) are working together to create a new social norm (the ‘11th commandment of gun safety’) that if someone is going through a bad patch (eg, his wife is divorcing him and he is drinking and talking crazy), it should be the norm for his friends to ‘babysit’ his gun until he feels better (eg, he gets a new girlfriend)—then he can have the gun back.6

  5. When young adolescent boys are killed accidently with a firearm, it is often at a friend’s house, where the boy’s friend has found and is playing with the dad’s handgun.38 The ASK campaign tries to instil a norm that the visiting boy’s parent will ask whether or not there is a gun in the home, and if so, whether it is stored securely.39 Advice columnists can weigh in on the importance of asking to protect your child’s safety.40

  6. Every year innocents are killed, when guns are shot in the air during celebrations, since ‘what goes up must come down’. While unlawful, celebratory fire still sometimes occurs. Sports heroes, and many others, could help make it clear that celebratory fire is just plain stupid.

  7. Hollywood movies, video games and our entire culture seem to admire the individual who can protect himself violently. By contrast, there is little appreciation for the far more effective and difficult skill of defusing hostile situations. Hollywood and others could begin to pay homage to the peacemakers rather than the unthinking warriors.

  8. Studies show that children are far more likely to know where the firearms are and to be able to access them than parents believe.41 42 Paediatricians, and many others, could do more to puncture the myth that hiding a gun (what some gun trainers currently advise) is an effective method of gun storage.43

  9. The National Rifle Association touts its Eddie Eagle program (‘Stop, Don’t Touch, Leave the Area, Tell an Adult’) as if it were an effective program and a sufficient one to keep children safe. The evidence shows it is neither.44 45 Many publications, including guides for home safety, could better relay the mantra of all injury professionals--that making the environment safe is far more effective than focusing predominantly on training children and expecting them never either to make mistakes or to behave inappropriately.

  10. Scientific studies of suicide have shown overwhelmingly that ready access to a firearm increases the likelihood of completed suicide in the USA. This fact is well known by suicide experts and firearm scholars,46 47 yet the lay public and many healthcare providers believe that if someone really wants to kill themselves, they will—a claim that is either a meaningless tautology or completely false.48 Healthcare providers, among others, could better inform themselves as to the facts and provide better advice to their patients. Indeed, I would argue that an American medical provider, working with the family to make a suicide prevention plan for an at-risk adolescent, who did not discuss firearms was committing malpractice.


All the examples in this paper focus on firearms. It is also important for students to understand that there are myriad potential ways to reduce firearm violence without doing anything about firearms—improving parenting, controlling anger, improving mental health, reducing binge drinking, reducing racism and so on. There are thus many more groups and government agencies that can play a role in reducing (firearm) violence, and many additional social norms that could be altered to reduce the problem. It is useful to point out that alcohol-related traffic fatalities have apparently been reduced more by seat-belt laws and airbags than by alcohol-focused interventions.49

In the post-Parkland environment, with the Florida high school students serving to help awaken America to the real possibility of reducing our firearm problems, many individuals and groups have been asking what they can do. I believe everyone has a role to play, and this class exercise helps students to understand that fact and to concoct new types of programmes. Most important, I believe it gives students a much better understanding of what is meant by the public health approach, an approach that is useful for firearms injury prevention, and for improving the public’s health in all areas.


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  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Patient consent Not required.

  • Provenance and peer review Not commissioned; externally peer reviewed.