Without context, a number is just a harmless configuration of scribbles symbolizing amounts – “315” on its own means nothing; it could be good or bad, a large amount or barely a drop in the bucket.

But with some context, that same number reveals a grim story: It’s how many people are shot every day in the United States. Another number, 96, is just as disturbing – that’s how many people die each day as a result of gun violence.

Gun-related crimes are rampant in many of our cities. Chicago is often in the spotlight due to its weekend flare-ups, but the police agency there and in other cities, including New Orleans, St. Louis, Detroit and Baltimore, actually battle gun violence on a daily basis.

Law enforcement agencies have their work cut out for them when it comes to lowering violent crimes – but some cities show us it’s possible. New York City, for example, was a dangerous place to live in the 1970s and 1980s – yet it began to turn things around in the 1990s, and now has the lowest violent crime rate of any major city in the country, attributed in very large part to policing tactics.

So what can other police agencies do to lower their own rates of violent crime? There is no one single answer, because a wide variety of strategies and tools are required to combat violent crimes – but one of the most important practices is a policy of comprehensive collection and analysis of ballistic evidence during investigations of crime scenes where shots were fired. 

What is Comprehensive Collection?

Comprehensive collection – the foundation on which successful ballistics analysis is built – means that every cartridge case is recovered from a scene, and every fired casing is entered into an evidence system, regardless of whether it was recovered at a drive-by shooting, a homicide or simply someone taking potshots at a stop sign.

This may seem like overkill, but it’s actually a major step toward being able to solve violent crimes and prevent future violence. When fired, a gun leaves distinctive tool marks on an ejected cartridge case. These marks are like fingerprints, in that they are unique to the gun that produced them.

Ballistics analysis programs and technologies allow officers recovering fired cartridge casings to upload images of the casings into a system containing images of other cartridge casings. The system’s analytics capabilities then scan the existing images and pull out potential matches – casings fired by the same gun. A technician or trained firearms examiner then can correlate the matches and hand the evidence over to investigating officers as a “lead” with potential value – important intelligence in any violent crime investigation.


Why Comprehensive Collection is Critical

The idea of comprehensive collection sounds straightforward and easy to implement and follow – but the unfortunate truth is many departments are not taking this approach due to an assumed lack of resources, or because they don’t fully understand why it matters.

Comprehensive collection is important because, for a ballistics analysis system to work at its highest capacity, every piece of potential evidence must be collected and accounted for. Ballistics analysis programs need images in the system to connect crimes, and the more pieces of evidence available, the likelier it is that a connection can be made.

When firearms experts review the cartridge case markings, he or she can determine if the recovered cartridge case is potentially linked to a cartridge case fired from a weapon used to commit another crime. The metadata created during the scanning of each cartridge case – including caliber, date, time and location – helps investigators to quickly connect cases.

These uploaded images also go into a national database of casings that help compare more crimes or shots fired. When law enforcement has a way to connect shots fired with no injury (e.g., celebratory gunfire), with crimes committed, they can get guns off the streets long before violent crimes occur. In a true nationwide sharing environment, a cartridge case in New York can be compared to historical cartridge cases in Los Angeles with the click of a mouse.

Matching cartridge cases and finding “potential link” correlations also help officers quickly determine how many firearms were present at a single crime scene. For example, if two .40-caliber and two 9-mm casings are recovered at a crime scene, analysis may reveal the two .40-caliber casings have similar markings, while the two 9-mm casings have different markings. This indicates that three different guns were used during this crime – a helpful piece of information for officers on the scene asking witnesses questions. A witness may say he or she only saw two guns, but that witness may either be mistaken, or be protecting someone.

Additionally, just because no one was harmed during a crime in which a gun was discharged doesn’t mean that cartridge is not also valuable. A homicide, vandalism involving a gun and a drive-by shooting in which no one was harmed all may have the same perpetrator and, with more information available via potential matches of different cartridges, investigators and analysts can connect more crime scenes, and then connect people to those scenes, opening up more possible leads that will solve crimes.

All Ballistics Evidence is Valuable

At the recent International Association of Crime Analysts annual conference, keynote speaker NYPD Chief Dermot Shea spoke about “precision policing,” a concept that focuses on the small amount of people responsible for the disproportionately high amount of crime. He also spoke of targeting organized narcotics gangs and violent serial offenders, and how investigators looking into these offenders shouldn’t leave any stone unturned – including the highly valuable practice of connecting gun crimes based on ballistic evidence left behind at the scene.   Chief Shea candidly said, “please don’t kick ANY cartridge cases down the sewer,” which translates to, “collect and invoice ALL ballistic evidence on every case.”  In other words, commit to the practice of comprehensive collection. 

Cities need improved strategies to support the men and women who attempt to prevent and ultimately investigate violent crimes. Comprehensive collection not only can help connect and solve cases, but it also can help interrupt the gun violence cycle. It should be a critical part of every investigative workflow so investigating officers can compare ballistics evidence from other crime scenes, generating more investigative leads, connecting more cases together, and getting violent offenders off the streets.