CO's gun laws: What is the impact so far?

Posted at 4:24 PM, Oct 02, 2015
and last updated 2015-10-02 18:24:43-04

Just days before the national gun control debate was renewed by Thursday’s horrific shooting at a community college in Oregon, the Federal Bureau of Investigation released data from Colorado’s first full year under new gun control measures.

The laws, passed in the wake of the Aurora theater shooting in July 2012 and the Newtown shooting in Connecticut in December 2012, went into effect during the summer of 2013. They included expanding background checks to cover more purchases and limiting new gun magazines to 15 or fewer rounds.

Earlier this week, the Federal Bureau of Investigation released its annual Uniform Crime Report covering the full year of 2014 — the first full year after Colorado’s new gun laws went into effect. The UCR is a great source for crime data because it uses a standardized format to compile information from all of the disparate law enforcement agencies across the nation.

Throughout this article, we will reference data from UCR data sets for 2012-2014. We’ll also examine a data set cataloging mass murders in the United States.

The questions to ask:

  1. Did Colorado’s new gun laws reduce the use of guns in crimes?
  2. Can the data show us anything significant about the impact of the new laws on mass murder in particular?
  3. Are murderers and mass murderers using the same kinds of weapons?

Before we examine those questions, we’ll start with an admission: It seems impossible to draw firm conclusions based on only one year of data in Colorado after the change in the laws — but there is only one year of data available at this moment in time. 

Data sources:


Question 1: Did Colorado’s new gun laws reduce the use of guns in crimes?

Across the nation, the percentage of murders, robberies and aggravated assaults involving guns fluctuated within about 1 percent per year during 2012-2014.

In Colorado, the data shows that the percentage of robberies involving firearms saw a slight decline over the three years. The percentage of aggravated assaults involving firearms increased slightly each year. 

Murders involving guns fluctuated in Colorado, with 2013 notably lower than either 2012 or 2014. It is the only category of crime in our collection of data that does not have a consistent year-to-year trend within the state of Colorado. 

But since 2013 was divided in half by the enactment of the new laws, let’s leave that out of our comparison. 

If you look at only 2012 and 2014, you’ll see an increase of 3.57 percent in murders involving guns.

The overall number of murders by firearm in Colorado was 91 in 2012 and was 92 in 2014, but the percentage of murder by firearms compared to all murders was higher in 2014 because the overall number of murders in the state was down during 2014. 

But consider that the 2012 data for Colorado includes a mass shooting in an Aurora movie theater, and the other years of Colorado data do not include such a crime. Is that a fair comparison?

If you subtract the 12 victims of that mass murder, 2012 would have had 80 murders with firearms. That arithmetic would reduce the overall number of murders and also the percentage of murders committed with a gun.

The new result, if you accept this equation, would reveal that 54 percent of murders in 2012 involved guns. It was 7 percent higher in 2014.


Question 2: Can the data show us anything significant about the impact of the new laws on mass murder?

First, let’s define mass shootings as involving at least four murders committed by a lone shooter, either in a spree or in a single location. That is the definition followed in a data set made available by Mother Jones.

In that measure, Colorado has not had another mass shooting since the murders in Aurora on July 20, 2012. In fact, Washington State is the only state to have two mass murder events since that date. 

But with a data set of just 13 incidents since July 20, 2012, there is hardly enough information to reach a conclusion. It is impossible to say if Colorado’s gun control efforts have had any measurable impact on the number of mass shootings, because there is no statistical basis for comparison. 


Question 3: Are murderers and mass murderers using the same kinds of weapons?

Continuing with the same definition, let’s examine Mother Jones’ data set of the weapons used by mass murderers. 

It reveals that 64 percent of the mass murder weapons used between 1982 and 2013 were either revolvers or semi-automatic handguns. Rifles represent 20 percent of the total. 

This is not drastically different than the rate of handgun use in murders in general. During 2014, 66 percent of Colorado firearm murders and 69 percent of US firearm murders involved handguns. 

The use of rifles, however, is drastically lower in overall murders. UCR data shows that is around 3 percent.

However, that is also difficult information to trust, since approximately one-third of the murders catalogued by the UCR data involved firearms of an unknown variety.