Memo on the Impact of Background Checks in Colorado

In July 2013, a new law passed requiring criminal background checks in Colorado for all person-to-person gun sales, with reasonable exceptions for family, hunting, and self-defense. The Colorado Bureau of Investigation (CBI), which conducts background checks and compiles numbers of those approved and denied, recently made some of this data publicly available. Everytown for Gun Safety analyzed this information, along with other measures of Colorado’s gun market. This memo provides the clearest picture to-date of how the expansion of the state’s background check system has improved public safety, including the following findings:

  • In the first eighteen months under the new law, CBI conducted 21,133 background checks for “private,” unlicensed gun sales of which 14,861 checks — more than two-thirds — were conducted at sites other than gun shows (and thus attributable to the new law).
  • These checks blocked 298 gun sales to criminals and other prohibited people — 100 for sales at gun shows and 198 for sales elsewhere — including people convicted of sexual assault, under restraining orders, and prohibited from possessing firearms due to severe mental illness.
  • By December 2014, monthly checks for unlicensed transfers at sites other than gun shows outnumbered those at gun shows 3 to 1.
  • Complying with the law is relatively easy throughout the state. At least 94.8 percent of Coloradans live within 10 miles of a licensed gun dealer that is conducting background checks on behalf of unlicensed sellers.
  • There is also evidence that unlicensed sellers have changed their behavior as a result of the law. Gun ads posted online by unlicensed sellers in Colorado are four times as likely to explicitly mention the words “FFL” or “background check” as ads posted in nearby states.


Support for the Second Amendment goes hand in hand with keeping guns out of dangerous hands. When felons, domestic abusers, and other categories of prohibited people obtain firearms, they pose an elevated danger to the public. Nearly half of gun criminals incarcerated in state prisons were prohibited from obtaining guns before their offense.Katherine A. Vittes, Jon S. Vernick, and Daniel W. Webster, "Legal Status and Source of Offenders' Firearms in States with the Least Stringent Criteria for Gun Ownership," Injury Prevention, June 23, 2012, doi:10.1136/injuryprev-2011-040290. Domestic abusers who acquire guns represent an especially potent threat: when a domestic abuser has access to a firearm, his partner has five times the risk of being murdered.Jacqueline C. Campbell, Daniel Webster, and Jane Koziol-McLain, "Risk Factors for Femicide in Abusive Relationships: Results from a Multisite Case Control Study," American Journal of Public Health 93, no. 7 (July 2003).

Background checks are the cornerstone of gun safety in the U.S. and the only systematic way to stop dangerous people from buying firearms. Since the creation of the National Instant Background Check System (NICS) in 1998, it has blocked more than 2.3 million gun purchases by prohibited buyers.The FBI releases a monthly report of Federal denials nationwide but does not publicly release data for individual states or over time. Between the inception of the NICS system in 1998 and July 31, 2014, 1,123,342 gun sales were federally denied ( In addition, between 1998 and 2010, state and local agencies issued a total of 945,915 denials, and it is estimated they have issued 225,000 denials in the three years since data was last released ( Thus, a total of more than 2.3 million federal and state denials have been made since the NICS system was implemented.

But this public safety law is compromised by a fatal loophole: In 33 states, criminals and other prohibited purchasers can avoid background checks by buying handguns or long guns from “private,” unlicensed sellers—often at gun shows or through anonymous online transactions—who are not required by federal law to conduct them. Nationwide, millions of guns are transferred each year without a background check.Licensed gun dealers conducted 9,856,984 background checks between December 2011 and December 2012 in the 38 states that did not, at that time, require background checks for unlicensed sales. Assuming that this number represents 60 percent of the total gun sales in those states, and private transfers represent the other 40 percent, an estimated 6.6 million private transfers took place over that same 12-month period.

How unlicensed sales arm criminals

It is common sense that if criminals are blocked from buying guns at licensed dealers but given an open door by unlicensed sellers, they will flock to that unregulated market, and the evidence confirms this. A survey of prisoners who committed crimes with handguns found that 80 percent got their guns through unlicensed transfers.U.S. Department of Justice, Bureau of Justice Statistics, Survey of Inmates in State and Federal Correctional Facilities, 2004, February 28, 2007. In 2013, a nationwide investigation of unlicensed online gun sales showed that 1 in 30 would-be gun buyers (3.3 percent) had prohibiting criminal records. That share is nearly four times higher than the share of buyers blocked by the background check system at licensed dealers (0.87%),Everytown for Gun Safety, Felon Seeks Firearm, No Strings Attached, September 2013, available at and subsequent investigations in Washington State and Vermont show that in some states the share of prohibited buyers may be as high as 1 in 10.Everytown for Gun Safety, Online and Off the Record, September 2014, available at; and Everytown for Gun Safety, Hiding in Plain Sight, January 2015, available at

Among the criminals shopping for guns online was a 27-year-old male in Fort Collins, Colorado, who posted an ad on March 30, 2013 seeking an M&P22 handgun. In 2005, the would-be buyer had attacked his ex-girlfriend and was found guilty of domestic violence harassment; he later violated an order of protection. Both offenses barred him from purchasing or possessing firearms.Domestic violence harassment is a prohibiting misdemeanor crime of domestic violence. C.R.S. §§ 18-9-111, 18-6-801. But at that time in the spring of 2013, there was nothing to stop him from evading the background check system by purchasing a gun in an unlicensed online sale.

Closing the loophole in Colorado

In November 2000, in the wake of the mass shooting at Columbine High School and after the state legislature had failed seven times to enact a gun violence prevention bill, Colorado’s voters passed by a two to one margin a ballot initiative requiring background checks for unlicensed guns sales at gun shows.Ballotpedia, “Colorado Gun Shows Background Checks, Initiative 22 (2000),” available at A dozen years later, the state’s legislators finished the job by passing HB 1229, which extended background checks to all unlicensed sales including those arranged online, with some exceptions, including gifts to immediate family members and some types of temporary transfers. As of March 2015, 17 states and Washington, DC require background checks for unlicensed handgun sales.

Ample evidence shows that closing this loophole saves lives. In states that require background checks for all handgun sales there are 46 percent fewer women shot to death by their intimate partners,Everytown for Gun Safety, “State background check requirements and rates of domestic violence suicide,” available at: 48 percent fewer law enforcement officers killed with handguns that are not their own,Everytown for Gun Safety, “State background check requirements and rates of firearm homicide against law enforcement,” available at: and 48 percent less gun trafficking.Daniel Webster, Jon Vernick, & Maria Bulzacchelli, “Effects of State-Level Firearm Seller Accountability Policies on Firearm Trafficking,” Journal of Urban Health, July 2009. To gauge gun trafficking, the authors measured the ratio of likely trafficked guns recovered from crime scenes to the total of guns recovered. A “likely trafficked gun” was defined as having been recovered at a crime scene and not in the possession of its original purchaser within one year of its last legal sale When Missouri repealed a requirement that gun buyers undergo a background check and obtain a permit before obtaining a handgun, the share of likely trafficked guns doubled and the gun homicide rate ballooned by 25 percent.Daniel Webster et al., "Preventing the Diversion of Guns to Criminals through Effective Firearm Sales Laws," in Reducing Gun Violence in America: Informing Policy with Evidence and Analysis (Baltimore, MD: Johns Hopkins University Press, 2013). Daniel Webster, Cassandra Kercher Crifasi, Jon S. Vernick, “Effects of the repeal of Missouri’s handgun purchaser licensing law on homicides,” Journal of Urban Health 91 no. 2 (March 2014); Daniel Webster, Cassandra Kercher Crifasi, and Jon S. Vernick, "Erratum To: Effects of the Repeal of Missouri’s Handgun Purchaser Licensing Law on Homicides," Journal of Urban Health 91, no. 3 (June 2014). Controlling for other factors, researchers estimate that the change in law was associated with an additional 68 gun homicides each year.

In this memo, Everytown reviews available data from the first eighteen months following the expansion of Colorado’s background check system to assess the impact of that change in law on public safety in the state.


The Colorado Bureau of Investigation (CBI) conducts background checks of would-be gun buyers in the state, and on a monthly basis publishes the number of gun sales by licensed gun dealers and by unlicensed sellers that were approved or denied.Colorado Bureau of Investigation, “InstaCheck Unit.” Would-be gun buyers who are denied may appeal the finding, and CBI also resolves these cases within 30 days.Colo. Rev. Stat. § 24-33.5-424(5)

CBI’s regular monthly reports provide insights about gun sales in the state, but they are limited in several ways. The reports do not indicate which unlicensed sales occurred at gun shows (and would have been subject to a background check by Colorado law even before the passage of HB 1229). They do not reflect denials that were appealed and ultimately reversed. And they provide no details about the reason the gun sales were blocked, although national data suggests that the majority of background check denials are issued to felons and domestic abusers.FBI, “Federal Denials,” accessible online at:

At the end of 2014, CBI conducted a more thorough review of its data related to background checks conducted over the past eighteen months. This data provides the clearest picture to date about how the expansion of the state’s background check system has improved public safety.

  • Number of checks: The data show that in the first eighteen months after passage of the HB 1229, CBI conducted 21,133 background checks for unlicensed sales of firearms, of which 14,861 checks — more than two-thirds — were conducted at sites other than gun shows.
  • Number of denials: Of the checks conducted for unlicensed sales, 298 were denied — 100 for sales at gun shows and 198 for sales elsewhere — and not subject to further appeal. The rate at which unlicensed sales were denied (1.41 percent) is slightly lower than the share of gun sales at licensed dealers that were denied over the same period (1.93 percent).Monthly data indicates that between July 2013 and December 2014 CBI conducted 456,385 background checks for sales at gun dealers, of which 8,794 resulted in denial.
  • Criteria for denial: CBI compiled data on the reason of denial for those issued in the first fiscal year after passage of the law. During that twelve-month period, CBI denied unlicensed gun sales at sites other than gun shows to 22 people convicted of assault or sexual assault, 18 people prohibited due to use of dangerous drug, 6 people under restraining orders, and 1 person prohibited due to mental illness.
  • Trends over time: The share of background checks accounted for by unlicensed sales rose throughout the time-period, and by December 2014 background checks conducted for unlicensed transfers at sites other than gun shows outnumbered those at gun shows 3 to 1.

Feasibility of conducting background checks

Under HB 1229, when an unlicensed seller and buyer want to transfer a firearm, they meet at a licensed dealer who conducts the background check before transferring the gun. All gun dealers are eligible to conduct these checks.ATF, “Open letter to all federal firearms licensees,” Jan. 16, 2013, available at: Many gun dealers across the country, including Colorado, take the additional step of listing themselves on the website as part of the market’s “FFL Holder Network,” attesting that they are “willing to handle firearms transfers for legal buyers.”GunBroker, “FFL SignUp,” available at As of December 2014, 485 licensed dealers in Colorado had listed themselves, 24% of the 1,987 total licensees in the state.

Using address data available from ATF,ATF, “Listing of Federal Firearms Licensees (FFLs) – 2015,” available at Everytown mapped these licensees and then estimated the share of Colorado’s population that lives within at least 10 miles of one of them.2 Everytown overlaid the data on population by census block group (CBG) over the period 2007-11 and then calculated the share of geographic area of each CBG that was within 10 miles of a dealer. On the assumption that that population density of each CBG is constant, the share of the geographic area of the CBG within 10 miles of an FFL approximates the share of the population of each CBG within 10 miles of an FFL. The analysis indicates that at least 94.8% of Coloradans live within 10 miles of a gun dealer who is conducting background checks for unlicensed gun sales.

Adoption by unlicensed online sellers

Background checks block gun sales to prohibited people but may further limit illegal access to firearms by deterring felons and other dangerous people from attempting to purchase guns at all. One indication of this is the change in how unlicensed sellers advertise firearms online. Everytown scraped ads offering firearms for sale or trade that were placed by self-described unlicensed sellers in Colorado and nearby states. Ads in Colorado were four times as likely as ads posted in the group of nearby states to explicitly include the words “FFL” or “background check.” This suggests a broad cultural change in how unlicensed sellers approach anonymous online sales.

Some criminals may still look for guns on the black market but research shows this is no substitute for the easy access provided by unlicensed sales. Contrary to conventional wisdom, obtaining guns on the black market is expensive and risky. Criminals report paying $250 to $400 on the black market for guns valued at only $50 to $100 in the legal market, the quality of firearms is uncertain, and conducting the transaction poses substantial risk of harm or arrest. A study of black market gun dealers found that more than one in three attempts to purchase a gun on the black market ended in failure.Philip J. Cook et al., “Underground gun markets,” The Economic Journal, 117, November 2007, F558-588.

Conclusions and Next Steps

This preliminary data offers evidence that the expansion of Colorado’s background check system has blocked gun sales to hundreds of criminals and other prohibited people, and that lawful participants in the firearm market — including unlicensed sellers offering guns online and licensed dealers conducting background checks on the behalf of their fellow citizens — are increasingly adopting the law. Colorado’s experience, and the data CBI collects and made available for this evaluation, may be instructive for other states like Washington, which enacted a law similar to Colorado’s in December 2014.

Further research will be necessary to measure how these changes in the behavior of law-abiding gun dealers and sellers impact criminal access to firearms and, ultimately, public safety. The experience of states like Missouri shows that changes in criminal access to firearms may be reflected in data on guns recovered by law enforcement and traced by the Bureau of Alcohol, Tobacco, Firearms and Explosives — particularly the state-of-origin and time-to-crime of the recovered guns. As of March 2015, aggregate trace data for guns recovered in Colorado were not available beyond 2013 for this type of analysis.ATF, “Firearms Trace Data – 2013.”

The CDC’s National Violent Death Reporting System (NVDRS) gathers data on the circumstances of firearm-related violence, and may provide another useful measure of changes in public safety. Colorado has participated in NVDRS since 2004, but as of March 2015, data are not available past 2011.CDC, “National Violent Death Reporting System,” available at

Additional research may also provide guidance to law enforcement about how to ensure state-wide compliance with the new background check law. Using the data that are currently available, it is not possible to assess how adoption of the law differs across the state. Statements made by some county sheriffs immediately after passage of the law indicated that enforcement of the background check requirement might vary regionally.Matt Stensland, “More Colorado sheriffs balk at gun-control measures,” The Denver Post, March 21, 2013, available at: A spatial analysis of background checks for unlicensed sales conducted to-date could confirm whether or not the volume varied significantly across the state’s 64 counties.

Click here to see an appendix of the data used in compiling this memo.