Legal issues related to preventing gun violence: Age-Related Firearm Restrictions and Safe Storage Laws

This is the fifth post in a series about Reducing Gun Violence in the United States. The previous post described Laws, the Second Amendment, Litigation, and Obstacles to Research and Policy.

In this post, I’ll explore age-related firearm restrictions and child access prevention laws.

Evidence for Age-Related Firearm Restrictions from Developmental Science

Federal Minimum Ages for Gun Purchases (source: Giffords Minimum Age)

In addition to the restrictions for owning firearms that we saw my previous post on gun laws, federal laws also include minimum ages for purchasing guns. For example:

  • Long guns (examples include rifles or shotguns): 18 years
  • Handguns: 21 years

Some states impose higher minimum age restrictions for purchasing guns.

Why do we have these restrictions? To answer that question, we need to look into what happens to people as they age from children to adults.

What’s going on during adolescence?

Three major changes occur during adolescence (source: Adolescent Maturity and the Brain)

  • Increases in novelty-seeking, or looking for new, exciting experiences
  • Increases in risk-taking: healthy risks like performing in concerts as well as unhealthy risks like using drugs
  • Increases in social affiliation, like building groups of friends or social circles

Brain Development in Childhood through Adulthood (source: How does the teenage brain work)

Current scientific understanding shows us that the human brain develops into the 20s and oftentimes well beyond these years. As seen above, the grey matter of the brain matures and gets denser as age 20 approaches (volume goes down but density goes up), generally starting from the back of the brain and moving to the front of the brain. The front of the brain, or the prefrontal cortex, is responsible for all kinds of logical behaviors such as delayed gratification, planning, and self-control. Put another way, those logical behaviors and skills develop more slowly than other skills that adolescents acquire.  (source: Giedd)

Connectivity in the Brain over Time (source: Neurobiology of the Adolescent Brain)

Another important area in the brain that is developing during adolescence is the striatum. The striatum regulates reward-seeking behavior and motivation. Something interesting to note about adolescent brain development is that the striatum matures much faster than the prefrontal cortex. The result of this is that the striatum is gets really good, quickly, at telling the adolescent brain “let’s go!” much sooner than the prefrontal cortex is getting good at saying “hmm, I’m not sure about that activity, let’s think about that a bit more”. In particular, the risks for misusing firearms show through clearly with more “let’s go!” thoughts and less “let’s think about that activity a bit more” thoughts.

During adolescence, some decisions that people make look at lot like mature, adult decisions, while others look much less mature. Situations in which adolescents often make less mature, juvenile decisions are called hot cognitive decisions, which are those impacted by a person’s emotional state. Those situations often involve peers, rewards, and emotional arousal, which are the same influencers which can trigger poor decision-making (sources: Adolescents Less Mature, Understanding Adolescence).

In short, changes happening inside the brains of adolescents increase the likelihood of making risky or dangerous decisions that impact themselves and others.

Adolescents react more to stress (source: Stress Response)

Adolescence is a critical time when any number of stressors impact our emotional lives. Things that happen during the adolescent years which add to this stress include: (sources: Regulatory Processes, Emerging Adulthood)

  • Transitions in relationships, jobs, education, and living situations
  • Less adult guidance and influence
  • Greater access to alcohol and drugs
  • Initial onset of common mental illness symptoms
  • Highest rates of suicidal thoughts, plans, and attempts

What does all of this have to do with firearms? Let’s go back to our picture of the minimum ages for purchasing firearms:

Age-related restrictions on firearm ownership are designed to prevent adolescents from mixing this risky period of transition with the lethality of firearms. The goal of these restrictions is to protect not only adolescents themselves but also the general public who might be put into harm’s way.

Child Access Prevention Laws

Child access prevention laws, or CAP laws, require gun owners to store firearms safely so that children cannot access them. Oftentimes, these laws have criminal penalties attached to them for gun owners who do not store their firearms in a safe manner.

Unfortunately, enforcement of these laws is spotty; often, they are not enforced until after someone is harmed by finding a gun stored unsafely in a house – law enforcement officers do not proactively monitor households for use of safe storage techniques.

The first CAP law took effect in 1989 in Florida, and since then, 18 states and the District of Columbia have passed safe storage laws. Even more states passed laws which prevent “furnishing” guns to minors without explicitly requiring safe storage. However, no safe storage laws have been passed in the last decade.

An important question to ask is: do these safe storage laws actually work to protect children? Several studies looked at this question, and the results show that safe storage laws:

  • reduce unintentional gun deaths
  • may be more effective if penalties are felonies rather than misdemeanors
  • are associated with a reduction in teen suicide


Evidence for Age-Related Firearm Restrictions from Developmental Science

  • Adolescents brains mature at a rapid and uneven rate
  • Brain areas which trigger reward-seeking behavior mature and take effect sooner than areas that are involved in planning and self-control
  • Age-related restrictions on firearms are designed to prevent adolescents from making dangerous decisions with firearms when they are most at risk to do so
  • Federal law creates age-based minimums for purchasing firearms based on this information

Child Access Prevention Laws

  • Child access laws (or safe storage laws) exist in 18 states and the District of Columbia
    • Though mostly unenforced until after an improper access
  • CAP laws reduce unintentional gun deaths and are associated with a reduction in teen suicide

Next upViolence, Alcohol, Drugs, and Guns


  • Giffords Minimum Age – Giffords Law Center Minimum Age to Purchase & Possess report
  • Adolescent Maturity and the Brain – a 2009 paper summarizing what is known about adolescent brain development
  • How does the teenage brain work – a 2006 article about teenage brain development
  • Neurobiology of the Adolescent Brain – a 2010 study focused on understanding how the brain is changing during adolescence relative to childhood and adulthood
  • Adolescents Less Mature – a 2009 study showing that adolescents demonstrate adult levels of cognitive capability earlier than they show emotional and social maturity
  • Understanding Adolescence – a 2012 report showing growing evidence pointing to the importance of changes in social and affective processing which are crucial to adolescent vulnerabilities
  • Stress Response – a 2009 study showing heightened physiological stress responses in typical adolescents
  • Regulatory Processes – a 2004 article highlighting clues from behavioral research on resilience to risks and assets, or vulnerabilities and protective factors in adolescence
  • Emerging Adulthood – a 2014 study showing that individual differences entering adulthood can present risks for psychological disorders

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Legal issues related to preventing gun violence: Laws, the Second Amendment, Litigation, and Obstacles to Research and Policy

This is the fourth post in a series about Reducing Gun Violence in the United States. The previous post described Firearms and Suicide.

In this post, I’ll explore federal, state, and local powers to regulate guns, the second amendment to the U.S. Constitution, litigation as a public health strategy, and obstacles to research, gun policy, and transparency.

Federal, State, and Local Powers to Regulate Guns

Governments can pass laws and create regulations to prevent gun violence. In the United States, these laws and regulations are created at the federal, state, and local level. As a civics refresher, there are three branches of government, each which play a different role in reducing gun violence:

  • the legislative, or law-making branch
  • the executive, or law-enforcing branch
  • the judicial, or law-interpreting branch

The Federal Government

Congress (the legislative branch of the federal government) only has powers that are granted to it by the Constitution. The Second Amendment to the Constitution, for example, limits the powers that Congress has with respect to guns – more on the Second Amendment below. Congress has passed three major pieces of gun-related legislation:

The Gun Control Act of 1968 described the basic method for regulating gun sales and firearm dealer licensing and added some new prohibitions for importing certain guns – only for use for sporting purposes. It also created some categories of people to whom guns could not be sold:

  • felons
  • unlawful users of illegal substances (drugs, for example)
  • people committed to mental institutions

The Firearm Owners Protection Act of 1986 reduced restrictions on selling guns without a license, which made private sales easier. It made it harder to convict dealers who sold guns illegally (and reduced penalties for doing so), and limited federal compliance inspections for licensed dealers. It banned computerized records of these inspections and banned federal government collection of firearms purchased and sold.

The Brady Handgun Violence Protection Act of 1993 created the background check requirement for licensed gun dealers and instituted the National Instant Criminal Background Check System, which went into effect five years later in 1998. It’s important to note that background checks were not created for private sales, but only if you purchased a gun from a retailer, like Walmart or Dick’s Sporting Goods.

Generally speaking, federal laws act as a minimum of gun restrictions, preventing some people from purchasing guns but not all. Here are some things federal laws do not do:

  • require background checks or record keeping for private sales
    • for example, selling a gun to someone you meet on Craigslist
  • regulate or prevent gun carrying in public

Federal Regulations

In addition to laws passed by the legislature, the executive branch (the “administration” headed by the President) may create agencies that create federal regulations. Federal agencies create rules and enforce laws passed by Congress. For example, the Federal Bureau of Alcohol, Tobacco, and Firearms regulates guns, but it is severely limited in its ability to do so by Congress’s laws. In fact, no federal agency has complete control over gun regulation, which makes it challenging to create meaningful restrictions at the federal level. This is in contrast to other products, such as cars, that the federal government regulates extensively through safety standards such as airbags, seat belts, highway safety, and so on.

State Governments

By way of the Tenth Amendment to the U.S. Constitution, those powers not granted explicitly to the federal government are reserved for the states. For example, one of the powers left to the states is police power – the ability for states to create police forces to protect the public. The police power is particularly important for preventing gun violence.

States can and do more with respect to gun laws than the federal government does; they may include extra restrictions or standards for ownership. In fact, most gun laws exist at the state level. Those laws might:

  • require training before purchasing a gun
  • prohibit those with violent misdemeanors from owning a gun (not just felons)
  • create a system for private sale background checks
  • register handguns or collect serial numbers
  • restrict who can carry a weapon in public
  • regulate the sale and ownership of assault weapons or smart guns (which can only be fired by authorized users)

Local Governments

Local (aka city, or municipal) governments have the least amount of power to regulate gun violence, but they feel the brunt of that violence themselves. They have police power, like state governments, but that power is granted by the state governments themselves and is often limited by something called preemption.

Preemption allows a state government to forbid local governments from passing certain laws. Most local governments are granted powers to protect their citizens, but local firearm regulations are often disallowed. For example, a state may prevent a city from passing their own gun regulations.

Only five states allow their local city governments to pass more strict firearms laws than state law. These states are:

  • Hawaii
  • New York
  • Massachusetts
  • Connecticut
  • New Jersey

The Second Amendment

The Second Amendment to the U.S. Consitution states that the right of the people to keep and bear arms shall not be infringed.

Sounds pretty clear, right?

It turns out that the full text of the Second Amendment is actually: “A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed.”

What does that mean? That somewhat convoluted text was written in the 18th century, and so it’s sometimes hard to figure out what the framers meant by this. So who gets to decide?

  • Advocacy groups, like the NRA or the Coalition to Stop Gun Violence? No.
  • The public? No.
  • The media? No.

The legal (and practical) reality is that the courts, or the judicial branch of the government, decides what this language means. It’s a very important fact, so it bears repeating:

The Second Amendment means what the courts say it means; not Congress, not the American public, not the media, and not advocacy groups.

Until recently, no federal court has ever struck down a gun law as violating the Second Amendment. For example, a law that the Supreme Court has not struck down as in conflict with the Second Amendment:

In 2008, a landmark court ruling by the Supreme Court in District of Columbia v. Heller did overturn Washington, D.C.’s almost complete ban on the right for people to own handguns in their own home. The court, in its ruling, voted 5-4 to strike down the law, saying that individuals have the right to have a handgun in their home for protection. However, it did not comment on whether individuals have the right to carry guns outside of their home, or how many guns they are allowed to own, or anything else. In fact, the Supreme Court went as far as to say:

“… nothing in our opinion should be taken to cast doubt on longstanding prohibitions on the possession of firearms by felons and the mentally ill, or laws forbidding the carrying of firearms in sensitive places such as schools and government buildings, or laws imposing conditions and qualifications on the commercial sale of arms.”

Lower federal courts and other state courts have upheld almost every other gun law – thousands of other laws – other than bans on private handgun ownership. Those laws which have been upheld as fully constitutional include restrictions on:

  • open-carry of guns
  • concealed-carry of guns
  • military-style weapons
  • high-capacity magazines
  • felons from owning guns

Still, the Supreme court has left many questions open on gun ownership. The big takeaway is that it has not interpreted the Second Amendment to prevent governments (federal, state, or local) from creating reasonable restrictions that promote public safety and help to keep guns out of the hands of people who are likely to harm others.

Litigation for Public Health

Litigation, or using lawsuits, is another way to protect public health. It can help to improve public health by financially incentivizing gun manufacturers and retailers to change the way that they create and market guns. Sometimes, litigation can even raise public awareness of the way that guns are made or marketed which can lead to new laws.

In the late 1990s and early 2000s, there were many lawsuits filed that targetted firearm manufacturers and dealers, some that were initiated by states and some by cities. Those lawsuits argued that gun manufacturers and dealers marketed their guns in a way that caused injuries (including death) and created other costs, and those lawsuits sought monetary damages. The costs, direct or indirect, included things like loss of economic value of life, lower property values, and emergency department fees.

If that sounds familiar, those lawsuits follow the same pattern of those that were filed against the tobacco industry years before and were largely successful.

There was a major reaction to these flood of gun lawsuits which was the creation of the Protection of Lawful Commerce in Arms Act of 2005. It severely undermined using litigation as a public health tool, as it provides broad protections to gun manufacturers and dealers from legal liability which almost no other consumer product in the U.S. market has. In addition to that protection, people harmed by gun violence have no legal remedy when they are affected – no pool of money is available to help victims of gun crimes, unlike, for example, persons injured by vaccines.

There have been some notable exceptions to the PLCAA’s power. For example, a lawsuit filed in the wake of the Sandy Hook shooting, Soto v. Bushmaster, alleged that the manufacturer of one of the weapons used in the shooting, Bushmaster, presented its marketing in an “unfair, unethical, or dangerous manner” and sought to “expand the market for [its] assault weapons through advertising campaigns that encouraged consumers … to launch offensive assaults against their perceived enemies”. The lawsuit was determined by the Connecticut Supreme Court in March 2019 to not be protected by the PLCAA, and is being allowed to move forward.

Obstacles to Research, Policy, and Transparency

Two particular laws have caused issues with research and policy development with regards to firearms. These are:

  • The Dickey Amendment of 1996
  • The Tiahrt Amendment of 2003

The Dickey Amendment

The Dickey Amendment is a provision first inserted into a 1996 federal spending bill, which mandated that:

While the Dickey Amendment only prevents money from being used for advocating or promoting gun control, it has also had a chilling effect on gun research at the CDC in general.

The Tiahrt Amendment

The Tiahrt Amendment is a provision of a 2003 federal money appropriations bill that

  • limits the availability and use of gun trace data, by prohibiting the ATF from releasing that data to anyone other than a law enforcement agency or prosecutor in connection with a criminal investigation.
  • prohibits the ATF from requiring gun dealers from doing inventories of their firearms as part of compliance inspections
  • requires the FBI to destroy firearm license background check data within 24 hours after a background check is complete

In 2012, a study of a specific gun dealer showed that the institution of the Tiahrt Amendment was associated with an increased level of guns flowing illegally from dealers to criminals, and at a higher rate.

Overall, these laws make it harder for researchers and policymakers to access data and make factual conclusions and recommendations about preventing gun violence. Even when individual state lawmakers have good policy ideas, law enforcement is restricted in its ability to implement those policies and trace guns used in crimes.


  • Gun laws are written at federal, state and local level, though federal laws are mostly bare minimums and state laws make up the bulk of gun laws
    • Most states prohibit cities from passing gun laws that are more strict than state law
  • The Second Amendment to the U.S. Constitution (the “right to bear arms”) means what the courts say it means
    • And this is disconnected from what many Americans believe that the Second Amendment means
  • Almost all gun laws have been deemed lawful and constitutional as long as they do not prevent a law-abiding person from owning a handgun in their own home for their own protection
  • All gun laws prohibit felons from having or owning guns
    • Additionally, individual states impose a variety of other constitutionally valid restrictions on gun ownership
  • Legislation is a powerful tool to prevent gun violence, but it also puts restrictions on how gun ownership, licensing, and crime trace data is used
    • The Dickey Amendment prevents the CDC from using federal money to advocate or promote gun control
    • The Tiahrt Amendment severely limits the availability of gun trace data, shields gun dealers from doing inventories of their guns, and forces rapid destruction of background check records at the FBI
    • These laws make it hard for researchers to determine what works best to prevent gun violence and prevents policymakers from implementing sound recommendations

Next up: Age-Related Firearm Restrictions and Safe Storage Laws

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Gun violence in the United States: Firearms and Suicide

This is the third post in a series about Reducing Gun Violence in the United States. The previous post described Gun Markets, Ownership, and Violence Risk.

In this post, I’ll introduce the relationship between firearms and suicide.

Background on Suicide

In 2017, there were around 24,000 firearm suicides in the United States; this accounts for half of all suicides during that year (over 47,000).

Suicide was the tenth leading cause of death overall, and the second leading cause of death for people under the age of 35 (source: CDC WISQARS).

The number of firearm deaths due to various causes looked like this (source CDC Wonder):

  • Suicide: 60% (23,854)
  • Homicide: 37% (14,542)
  • Legal Intervention (typically due to law enforcement activities): 1.4% (538)
  • Unintentional: 1.2% (495)
  • Unknown: 0.8% (338)

Suicide rates vary dramatically across the various states, with some states having as many as four times the number of suicides as other states:

Suicide Rates in the United States (source CDC WISQARS)


The following graph sorts the states left to right; states with highest levels of self-reported emotional and psychological well-being on the left, and those with lowest levels on the right. States with the highest suicide rates are not those states which have the lowest levels of emotional and psychological well-being. On its face, this is a puzzling result.

Suicide rates (age-adjusted) related to rates of well-being (source Gallup Well-Being)


Let’s continue looking at the rates of firearm ownership and suicide, firearm suicide, and non-firearm suicide across several states. What we see is that

  • the more firearms are owned in the state, the higher the rate of firearm suicide
  • the more firearms are owned in the state is not related to the number of non-firearm suicides
  • rates of suicide overall are much higher in states with more gun ownership

Rates of firearm ownership and suicide (source: Firearms in the Northeast)

Let’s take a look at acts where people try to harm themselves:

  • Most people attempting to harm themselves do so by poisoning, cutting, or piercing (85%)
    • Poisoning, cutting, and piercing only result in fatal injuries 3% of the time
  • Very few people attempting to harm themselves do so using firearms (5%)
    • Use of a firearm in self-harm results in a fatal injury 91% of the time

In short, when people use a firearm to hurt themselves, they are very, very likely to end up with a fatality.

Deliberate Self-Harm and Case Fatality Rate by Act, Seven Northeastern states, 1994-2000 (source CDC WISQARS and HCUP-NIS)

Looking at the data another way:

  • Those people whose suicide attempt was successful had used a firearm in more than half of cases
  • Those people whose suicide attempt was unsuccessful had used poison or an overdose 83% of the time

A key insight is that if access to firearms is difficult for people in a crisis where they are considering suicide, they are more likely to use a different method, which is much more likely to result in a life being saved.

Methods of Self-Harm (source CDC WISQARS and HCUP-HIS)

When reviewing cases of survivors of suicide attempts, we find some interesting other information:

  • suicidal acts are typically impulsive, and the thoughts that lead to those acts are typically temporary
  • the choice of suicide method is largely dependent on the availability of that method (such as a gun)
  • less than 10% of suicide survivors re-attempt suicide a second time
    • so if we can lessen the risk of a successful first suicide attempt, those people are much, much more likely to survive long-term

Saving a person who has suicidal thoughts today means very likely saving their life in the long run.

Data-driven Studies

How do we know that firearms availability actually is a cause of increased suicide risk, rather than just being correlated with it?

More than a dozen studies between 1991 and 2005 show that having a firearm in a home greatly increases the risk of suicide for all members of the household, especially young adults and children. These studies controlled for age, alcohol usage, community, depression, education, illegal drug use, medication usage, and mental health diagnosis.

Accessibility of Firearms and Risk of Suicide Among Household Members (source: Accessibility of Firearms)

Suicide rates do not vary much per state, but rates do have to do with the availability of firearms in the home. Between 2008 and 2009, there were over 11,000 suicides in states with high gun ownership rates vs about 6,000 suicides in states with low gun ownership. The rate of suicide attempts overall did not vary from high to low gun ownership states.

Is Risk Independent of Underlying Suicidal Behavior? (source: Risk Independence of Suicide)

There is also a strong relationship between safer storage of guns in the home and lower rates of suicide for youth. Note how the rates of suicides in cases with guns stored unlocked (unsafely) is more than twice that of rates of suicides with guns stored safely (locked).

Firearm storage practices and suicide risk for 5 to 19-year-olds (source: Gun Storage Practices)

Let’s return to the topic of what we know about these guns that are in people’s homes:

  • Around 265 million firearms are in the hands of civilians (source: Stock and Flow)
  • 1/3 of US households own guns (estimate) (source: Stock and Flow)
  • 5 million children live in homes with guns (estimate) (source: Firearm Storage with Children)
  • Firearms are the most lethal method of commonly completed suicides (source: Case Fatality Rates)
    • The majority of the guns used in these suicides come from the victim’s homes (source: Self-Inflicted Injuries)
    • More than 90% of these guns have been in the home for more than two weeks, often years (source: Suicide in the Home)
  • Gun owners and members of gun-owning homes are neither more depressed nor any more suicidal than members of non-gun-owning homes (source: Recent Psychopathology)
  • No likely factor yet unstudied can account for the strong relationship between firearm availability and suicide (source: Are We Missing Something?)

There are success stories for suicide prevention based on empirical data. Here is one from the Israeli military. In the early 2000s, the Israeli military noticed that many service members were committing suicide, mostly during weekends with their service weapons. In 2006, the Israeli changed their firearm policy to prevent service members from taking their guns home on the weekend.

The result? (source: Decrease in Suicide)

  • Suicide rates dropped by 40% over the weekend
  • Suicide rates during the week remained unchanged

Are we using this data that we know?

As seen above, strong evidence exists that firearms do play a direct role in increasing suicide risk. Are we actually using this information?

A survey of emergency department employees, doctors, and nurses who worked with suicidal patients were asked if they thought restricting access to firearms would affect the suicide rate. They were asked the question:

“Had a firearm not been accessible to them, how many do you think would have found another way to die by suicide?”

The results were that a large fraction thought that most or all of the firearm suicide attempters would have found a similarly lethal way to die by suicide if their firearms had not been available (which we know is not true by the data presented above):

  • 67% of nurses
  • 43% of attending physicians
  • 44% of resident physicians

Would suicide victims have died by another means if firearms were not available? (source: Lethal Means Restriction)

Those healthcare providers were then asked if they asked suicidal patients if they had firearms in their home.

  • only two-thirds asked when a patient said they were suicidal and had a plan to use a gun
  • less than 20% asked when a patient said they were suicidal but did not have a plan with a gun

Do you ask if firearms are at home? (source: Lethal Means Restriction)

In fact, when surveyed, most Americans do not think that restricting access to guns will have an effect on suicide rates, and they also show broader disbelief about restricting access to lethal means of suicide:

Does a gun in the home increase the risk of suicide? (source: Suicide Relationship Belief)

Generally speaking, members of the public do not believe the reality of the data about suicide prevention which shows that having a gun at home substantially increases the risk of suicide, both for the owner themselves and other household members.


Background on Suicide

  • 60% of people in the US who are involved in firearm violence die due to suicide (almost 24,000 people)
  • Suicide rates are not correlated with general well-being
  • Suicide rates are significantly higher in states with higher gun ownership
  • Most people attempting to harm themselves use non-fatal methods (> 80% of the time)
    • But people using firearms in a suicide attempt will succeed more than 90% of the time
  • Only 10% of suicide survivors go on to attempt it again later
    • So saving someone’s life today from suicide means very likely saving their life in the long run

Data-driven Studies

  • Many studies confirm that the availability of firearms cause an increase in suicide rates (not only correlation)
    • Especially affects young adults and children when firearms are in the home
  • Rate of suicide attempts does not vary from high to low gun ownership states
  • Gun owners and members of gun-owning homes are neither more depressed nor any more suicidal than members of non-gun-owning homes
  • Firearms in the home are a major contributor to the 47,000 suicide deaths that occur in the US every year

Are we using this data that we know?

  • Members of the public do not believe the reality of the data about suicide prevention which shows that having a gun at home substantially increases the risk of suicide, both for the owner themselves and other household members
    • This includes medical professionals such as emergency department personnel who see suicidal patients on a day to day basis

Next up: Laws, the Second Amendment, Litigation, and Obstacles to Research and Policy


  • CDC Wonder – a public resource of health-related datasets for CDC staff, public health departments, researchers, and the general public. The year 2017 is the most recent year for which comprehensive, compiled data exists for firearm violence
  • CDC WISQARS – a public database that provides fatal and nonfatal injury, violent death, and cost of injury data.
  • Gallup Well-Being – results from the 2019 Gallup poll on well-being in all 50 US states
  • Firearms in the Northeast – a research study from 2004 on whether firearm availability increases the overall number of suicides rather than the proportion of suicides from guns
  • HCUP NIS – Healthcare Cost and Utilization Project National Inpatient Sample is the largest publicly available all-payer inpatient health care database in the United States, yielding national estimates of hospital inpatient stays. Data from 2005 was used.
  • Accessibility of Firearms – a 2014 study to understand estimates of the association between firearm availability and suicide or homicide
  • Risk Independence of Suicide – a 2013 study looking at the risk independence of suicidal behavior
  • Gun Storage Practices – a 2005 study measuring the association of specific household firearm storage practices and the risk of unintentional and self-inflicted firearm injuries
  • Stock and Flow – results from the 2015 National Firearms Survey
  • Firearm Storage with Children – results from a nationally representative probability-based online survey sample of US adults conducted in 2015
  • Case Fatality Rates – a 2004 study examining how method-specific case fatality rates for suicide differ by age and sex
  • Self-Inflicted Injuries – a 1999 study to determine ownership and usual storage location of firearms used in unintentional and self-inflicted intentional firearm deaths and injuries
  • Suicide in the Home – a 1992 study to assess the strength of the association between the availability of firearms and suicide
  • Recent Psychopathology – a 2009 study to assess the relationship between firearm ownership and possible psychiatric confounders of the firearm–suicide relationship
  • Are We Missing Something? – a 2016 study to determine the plausibility of some unaccounted variable in determining the causal relationship between firearm availability and suicide
  • Decrease in Suicide – a study of the effects of a policy change in the Israeli Defense Forces reducing adolescents’ access to firearms on rates of suicide
  • Lethal Means Restriction – a 2013 study examining the beliefs and behaviors of emergency department providers related to preventing suicide by reducing suicidal patients’ access to lethal methods
  • Suicide Relationship Belief – a 2017 study using nationally representative sample to describe public opinion about whether household firearms increase the risk for suicide

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Gun violence in the United States: Gun Markets, Ownership, and Violence Risk

This is the second post in a series about Reducing Gun Violence in the United States. The previous post described Impact, Trends, and Defensive Use.

In this post, I’ll explore the various legal and illegal methods in which people acquire guns, as well as the risk of violence due to that gun ownership.

Now, let’s dive into gun markets and ownership.

Legal and Illegal Gun Markets

Almost every gun used in crimes in the United States was first acquired through a vendor with a federal license to sell firearms. The US Bureau of Alcohol, Tobacco, and Firearms (ATF) automatically receives information about each and every gun that is sold and anytime local, state, or federal law enforcement officers recover a gun from a crime scene or criminal suspect.

Each gun has a unique serial number, which identifies the make, model, and caliber, and can be used to trace where the gun was originally purchased.

Here are some examples of serial numbers on guns:


The ATF has a great flow chart showing how guns enter the illegal market:

How Guns Flow from Legal to Illegal Commerce

Legal Trade in Guns

  • Starts with gun manufacturers
  • Guns are sold to dealers
  • Those guns are sold to law-abiding gun owners
  • Guns may then be re-sold in legal private sales

Guns enter illegal commerce in several ways (some examples):

  • By private transactions in which guns are bought and later sold to prohibited people at gun shows, flea markets, or through private sales
  • By straw purchasers, who are individuals who buy guns from dealers and transfer them to prohibited people
  • By theft, where firearms are stolen from gun dealers and private citizens

Now, let’s take a look at how many guns enter the market illegally via different avenues. Note how the number of firearms (N firearms) being sold or otherwise transferred by federally licensed dealers without reporting to the ATF (largely to gangs and other criminals) is greater than those for straw purchasers or private sales. It also dwarfs the number of firearms stolen or those obtained via filling out paperwork illegally.

Data from Federal Firearms Trafficking Investigations, 1999-2002 (source: Illegal Gun Market)


When looking at sources of firearms reported by state and federal prison inmates, the largest share of those guns were acquired illegally through the underground market, not through legal purchases, gifts, theft, or buying for someone else. It’s important to note that the “underground market” could mean many things: traffickers selling guns state to state, selling a gun on the street which was stolen from a car, or many other things.

Source of firearms used in crimes by State and Federal prison inmates, 2016 (source: Source of Firearms)

While prison inmates report that only 6% of guns are acquired via theft, an estimated 350,000 – 400,000 firearms are stolen every year. The majority of guns stolen come from Southern states. These Southern states account for (source: Whose guns are stolen):

  • 37% of homes with guns
  • 43% of gun owners
  • Two-thirds of all guns stolen

Additionally, higher gun theft risk is associated with (source: Whose guns are stolen):

  • owning six or more guns
  • carrying a gun in public
  • storing a gun in a vehicle

Gun Ownership and Violence Risk

When a person is involved in an assault, the availability of a firearm can increase the severity of any violent actions. One big reason that having a firearm available to someone who might consider committing a violent act might increase the chance of that act occurring is that possessing a deadly weapon as an assailant lowers their risk of injury. After all, if one is going to break into a person’s house and they have a gun, they’re probably going to face less resistance than if they just have their own fists.

If you, as an assailant with a gun, have less resistance in committing a crime, wouldn’t there be less chance of physical violence occurring? Or, if you protect yourself with a gun, aren’t you less likely to come to any harm because you have a deadly weapon which can protect you? Unintuitively, it turns out there is evidence that having a firearm could actually cause a more dangerous attack from someone who is armed.

It’s not difficult to imagine how this situation turns into a chain reaction, where potential criminals begin to carry more and more dangerous weapons, and if you’re a person concerned with lethal violence in your community, you begin to carry more deadly weapons such as guns yourself.

Reflecting on this, an important question to ask is:

Does keeping a firearm in one’s home increase, decrease, or have no effect on the risk of gun homicide in the home?

A few different studies in the US have led to some important observations (sources: Gun Ownership as a Risk Factor, Handguns and Firearm Violence, Risk Factors for Femicide)

  • In 77% of firearm homicide crimes, the offender and victim knew each other
    • Often, they lived in the same house
  • In only 3.7% of firearm homicide crimes was the victim a stranger to the offender
  • Having a gun in the home increased the firearm homicide risk by anywhere from 40 – 170%
  • Women in physically abusive relationships living in a home with a gun increased their risk of being a homicide victim by 400%

So, most often, gun homicide is a result of some kind of conflict in a home. Similarly, having a gun the home dramatically increases the risk of firearm homicide, especially for women as victims.

Another interesting question we can ask is:

Are people who purchase handguns legally more likely to be violent offenders?

A 2010 study in California found that after purchasing handguns (source: Violence Criminal Activity):

  • 1% of purchasers who had no previous criminal record committed a violent crime
  • 5.5% of purchasers who had a previous felony or violent misdemeanor conviction committed another violent crime

So, if one has a previous violent crime conviction, they’re over five times more likely to commit another violent crime after purchasing a handgun

For all people purchasing handguns,

  • Conviction rates for serious violent crimes for those without a previous criminal record were lower than the general population
  • Conviction rates for serious violent crimes for those with a previous criminal record were much higher than the general population

An important takeaway: law-abiding gun owners are even more law-abiding than the average person. But, those people that have serious criminal histories are at much higher risk for future offenses.

Looking at states with the lowest to highest rates of gun ownership (first through fifth quintiles in the left-most set of colored bars below), states with the highest rates of gun ownership show the highest rates of gun assaults. The rates of homicides with guns also increase, but not as dramatically.

Gun Assault Rate Ratio for Gun Ownership (source: Firearm Ownership in the US)

Reflecting on this, if there is more violence with places that have more guns, why is this? Is it something about the place itself, or does it have to do with the individuals who own guns?

Two different studies showed that:

  • States with the highest rates of gun ownership sold more guns that were eventually used in crimes than states that had more restrictive gun laws and lower gun ownership rates
  • All other factors being equal, homes with more guns had higher rates of burglary.
    • Theory: could this be because thieves know that guns have a high street value or personal value for other crimes?


Legal and Illegal Gun Markets

  • The US Bureau of Alcohol, Tobacco, and Firearms (ATF) tracks firearm transactions through unique gun serial numbers
  • Illegal firearm acquisition occurs through various means
    • ~38% through illegal diversion from federally licensed dealers
    • More than straw purchasers (21%), illegal private sales (21%), theft (8%), or lying on background check / licensing forms (4%)
  • Most guns used in crimes reported by prison inmates came through the underground market
    • Only 10% obtained via direct purchase from a gun dealer
  • Majority of guns are stolen from Southern states (two-thirds)
    • Higher incidents for people owning six or more guns, carrying them in public, or storing them in a vehicle

Gun Ownership and Violence Risk

  • Gun availability affects violence, including lethal violence, in many ways:
    • Risk of domestic violence goes up dramatically when a gun is in a home
    • Criminal offenders owning a gun are at higher risk for future offenses
    • More guns available in the home opens up opportunities for theft and future violence
  • Most people who own guns are responsible owners who are law-abiding citizens
    • Yet the risk of violence and threats to safety are still greater overall for gun owners, even if they are safe gun owners

Next up: Firearms and Suicide


  • Illegal Gun Market – a 2012 study interpreting the empirical evidence on illegal gun market dynamics
  • Source of Firearms – a 2016-2019 study of the source and use of firearms involved in crimes via a survey of prison inmates
  • Gun Ownership as a Risk Factor –  a 1993 case-control study of homicides in homes in three metropolitan areas in the United States
    • There was some criticism of this study and its design; one prominent criticism being that the chance of the estimated associations between homicide risk and firearms may be biased since the cases and controls were different from each other with respect to risk for violence overall
  • Whose guns are stolen – a 2017 examination of demographics and behavioral characteristics of gun owners who report having guns stolen
  • Handguns and Firearm Violence – a 1997 study of the association between the purchase of a handgun and homicide or suicide
  • Homicide and Suicide Risks – a 2003 study of homicide and suicide risks associated with firearms in homes
  • Risk Factors for Femicide – a 2003 study of risk factors for femicide in abusive relationships
  • Violence Criminal Activity – a 2010 study of incidence and risk factors for violent criminal activity among prior gun purchasers
  • Firearm Ownership in the US – a 2015 study of the association between state-level firearm ownership and violence crime

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