Nearly 12,700 homicides were committed with weapons — 8,583 with firearms — in the United States in 2011, according to FBI data. Of the murders where firearm types were identified, 6,220 were committed with handguns; 323 with rifles; and 356 with shotguns. Another roughly 1,700 were committed with firearms either of unknown type or in other categories. Data from the Centers for Disease Control and Prevention (CDC) shows that 81,363 people were injured by firearms in 2012, although statistics about wounded persons are known to be incomplete.

Behind these figures are a variety of significant cultural trends and shifts, as well as myriad efforts by law enforcement across the country employing different tactics and strategies.

First, there is a long-term trend toward fewer violent crimes and murders across the population: Since 1991, the rate of violent crime has been cut nearly in half, according to FBI data. In May 2013, the Pew Research Center issued a report titled “Gun Homicide Rate Down 49% Since 1993 Peak; Public Unaware.” Despite differences in numbers, both FBI and CDC researchers agree that the overall number of gun-related murders has declined in recent years. (For more on this varying data, see this post from Annenberg Public Policy Center’s FactCheck.org.)

Despite shocking rampage violence in places such as Aurora, Colo., and Newtown, Conn., some scholars have argued that there is actually a declining culture of violence and guns in America. U.S. gun ownership rates have also declined in recent decades, going from about 50% in the 1970s to 34% in 2012, according to a New York Times analysis of General Social Survey data. Yet a 2011 study in the Journal of Trauma from Harvard and UCLA compared the United States with similar nations and found that U.S. homicide rates were “6.9 times higher than rates in the other high-income countries, driven by firearm homicide rates that were 19.5 times higher. For 15- to 24-year-olds, firearm homicide rates in the United States were 42.7 times higher than in the other countries.”

This crime data has also been playing out against political shifts: In recent years the public has been roughly split over whether gun regulation or rights are more important; this follows a long period where the majority favored regulating guns, according to Pew Research Center data. However, the Newtown, Conn., school shootings appears, for the first time in years, to have shifted public opinion back toward increased support for some gun control, according to a New York Times/CBS poll. A 2013 survey and report published in the New England Journal of Medicine has data on the public’s views on guns, mental illness issues and violence, in the wake of the Newtown; overall, it also shows a greater embrace of gun restrictions.

A 2013 study published in the journal Internal Medicine — from the American Medical Association — examined the strength of laws across the 50 states and looked at the relationship with the number of homicides and suicides over the period 2007-2010. The study found that “higher number of firearm laws in a state are associated with a lower rate of firearm fatalities in the state, overall and for suicides and homicides individually.” However, the researchers admitted that the precise relationship could not be established, and a related comment published by an independent researcher underscored the study’s limits. Another 2013 study, from Johns Hopkins, looks at the same problem by isolating specific cases of gun violence in different states; its conclusions are also mixed, though the researchers do note that “stricter gun ownership laws in states with the lowest standards would have made firearm possession illegal for many who used a gun to commit a crime.”

As trauma surgeons and first-responders are well aware, the precise type and capacity of weapons can matter a great deal in terms of damage done to the human body. Though assault weapons are used in relatively few incidents, some researchers suggest that their prevalence likely “amplifies pre-existing risks of violence.” Further, the availability of semi-automatic pistols, for example, likely drives up homicide rates, compared with more conventional revolvers, according to researchers at the University of Pennsylvania.

Scholarship on the effectiveness of the 1994 assault weapons ban — which expired in 2004 — has suggested that the law may have reduced gun-related homicides in the immediate aftermath of the law’s passage, but gun market forces (particularly the increase in manufacturing just prior to the ban) complicate this picture. Researchers believe that the failure to curb the use of large capacity magazines, also technically banned by the new law, muted the law’s intended effects. As noted in a 2004 study from the University of Pennsylvania’s Jerry Lee Center for Criminology, the use of assault weapons — primarily assault pistols — in gun crimes after the 1994 ban was implemented dropped by 17% to 72% across cities such as Baltimore, Miami, Milwaukee, Boston, St. Louis and Anchorage. However, assault weapons were used in only 2% to 8% of gun crimes before the ban; by far the most pressing issue was the use of large capacity magazines, which were used in 14% to 26% of gun crimes before the ban. The use of these magazines continued at high rates. The scholars conclude that the millions of pre-existing (“grandfathered”) assault weapons and large capacity magazines in private hands diminished the power of the ban in the short term, and they suggest that the ban’s 10-year duration was not yet long enough to see significant changes.

A 2000 study titled “Homicide and Suicide Rates Associated with Implementation of the Brady Handgun Violence Prevention Act” found that implementation of mandatory waiting period for gun purchases through licensed gun dealers and mandatory background checks yielded mixed results. The study, from Georgetown University, found that these new rules were “associated with reductions in the firearm suicide rate for persons aged 55 years or older but not with reductions in homicide rates or overall suicide rates.”

As suggested, the research area focusing on firearms and the reduction of violence is complex; psychological, social and cultural factors all play a role, and policy solutions have not proven easy, in general. Research findings in this area are also typically mixed and context-specific. However, a 2012 study from Arizona State University and the University of Cincinnati published in Crime and Delinquency, “The Effectiveness of Policies and Programs That Attempt to Reduce Firearm Violence: A Meta-Analysis,” reviewed the effectiveness of dozens of policies designed to reduce gun violence in the United States. The researchers examined 29 rigorous studies between 1983 and 2005 that assessed the effectiveness of four major areas of gun violence interventions: information, training, and storage campaigns; gun buy-back programs; gun laws; and law enforcement campaigns.

Key study findings include:

• “The studies included in this analysis, on average, indicated a weak to moderate impact of these policies and programs on gun violence.”
• While all interventions reduced gun crime, gun buy-back programs and stricter gun laws were found to be only marginally effective. Law enforcement efforts, however, were found to significantly reduce gun-related crimes.
• Of these legal interventions, probation strategies — increased contact with police, probation officers and social workers — proved most effective at curtailing gun violence; policing strategies and community programs were moderately effective, while “prosecutorial strategies” — harsher sentences and restricted bail opportunities — showed the least promise.
• Mandatory firearms waiting periods and background checks were shown to have no statistical effects on gun crimes, while bans on specific weapons were moderately effective.
• “The effect of safe-storage laws show they have been ineffective at reducing gun crime. The [studies] examined … found that, if anything, safe storage laws work to increase crime.”

The researchers conclude that “law enforcement programs are clearly more effective than gun laws.” They note that the “most effective programs combined both punitive and supportive strategies to effectively reduce gun violence…. The assessment of [gun violence prevention programs] provides clear guidance concerning which approaches are most likely to result in enhanced public safety — an outcome that should be attractive to policy makers regardless of their ideological persuasion.”

It is worth noting that research findings in this area are of more than just theoretical interest. Two of the country’s leading jurists, Supreme Court Justice Stephen Breyer and U.S. Court of Appeals Judge Richard Posner, have recently reviewed the academic literature and incorporated it into their opinions (Breyer here, and Posner here) on gun restriction-related cases, as the New York Times notes. Both jurists found that the empirical research is not conclusive enough to support certain kinds of gun restrictions, specifically a ban on carrying guns in public.

Keywords: crime, guns, law, metastudy, youth, policing