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Gunfire Detection: The Complete Rundown

More than 70 municipal police departments in the United States are deploying gunfire detection technology that uses a web of wirelessly connected acoustic sensors posted on roof tops and light poles to alert dispatchers when shots are fired much more rapidly and consistently than civilian calls to 911.

The technology behind gunfire detection systems emerged from the military in the 1990s, where it was used to find snipers. It involves placing the sensors to create a net that encompasses a targeted area. The sensors are able to operate wirelessly, sync with other technology such as cameras and can distinguish gunfire from other sounds.

The sensors use GPS to pinpoint the exact location of the shot and notify police to send units to that location. As an investigative tool, the systems prove valuable in establishing a chain of events and where they took place.

Diagram explaining how the ShotSpotter works
Image provided by ShotSpotter

Analyzing trends in gun-related activity is made easier as systems allow police departments to keep track of the amount of gunfire in an area by creating maps of data which show every time a weapon is discharged and where.

An additional upside of the technology for police departments is the potential to provide an accurate record in cases where officers are accused of opening fire on civilians. Recordings from sensors are often able to distinguish the caliber of the weapon fired, the position it was fired from and exactly when it was fired.

A variety of vendors offer the technology, the cost of which varies on the size of the area departments want to monitor. A popular vendor that’s made headlines as more cities adopt it is SST, Inc., based in California. ShotSpotter (SST), as it is alternately known, detected more than 51,000 gunshots in the United States in 2013 according to its website.

By potentially decreasing response time to gun-related incidents and increasing the number of tools departments have available for investigations, this technological advantage in fighting crime is giving police plenty to think about.

What Does It Cost?

The size of the area police want to cover determines the number of sensors and degree of monitoring and maintenance involved. For this reason, high crime areas are generally prioritized.

In the case of New York City, which announced in 2015 that it will implement SST, the cost is estimated at $1.5 million annually. The system becomes the latest branch of the city’s “Domain Awareness System”, a network of gunfire detectors, surveillance cameras, license plate readers, social media and GIS.

For smaller cities not looking to cast as wide a net, the cost usually ranges in the hundreds of thousands. But the price doesn’t end at installation.

High tech systems such as SST require maintenance, adjustments and updates. The cost of that varies as well. In the case of New Haven, Connecticut, which purchased the system in 2009 for $374,000, maintenance cost the city an additional $98,000 over the first four years of operation, according to a news report by Fox CT television based in Hartford, Connecticut.

The Debate: Does It Work?

Critics say the money being spent on these systems could be used to put more cops on the street. Meanwhile, proponents argue that the technology makes the current police force more efficient.

Law enforcement officials are split between the status quo and an investment in a technology that may become ubiquitous for police departments nationwide in the future, the way radar guns are today.

For some markets, particularly those that have witnessed growing pains of the technology, the detection systems have been wildly inefficient at times.

In New Haven, for example, during the spring of 2012, police records show that out of 60 alerts registered by the system, only six were confirmed, giving it a success rate of 10%, according to the Fox CT news report. One year later, the success rate fell to just 8%.

The company said a number of New Haven’s problems came from employing the system before it was tested and calibrated.

Many of the problems surrounding false positive alerts, however, were mitigated after SST reps flew to New Haven and adjusted the system. With each passing year, systems become stronger and are now being aided by vendor companies working with the police.

Subscription/Remote Monitoring Services

A major factor in the recent improvements to gunfire detection results is a verification service offered by vendors such as ShotSpotter. If police departments subscribe to the service, the sensors send the alert to an acoustics analyst in a control center at the company’s headquarters. The analyst listens to the sound and within seconds can determine whether it is an actual gunshot or some other disturbance such as fireworks before notifying police.

This service can reduce false positives, making the detection networks more reliable tools for cities that have struggled with implementation.

What Do Citizens Think?

When the Oakland, California, police department proposed killing its ShotSpotter program in March of 2014 due to concerns about the cost of renewal, residents felt the police were prioritizing saving money over saving lives.

For those in neighborhoods where police presence is viewed as inconsistent, the sensors’ ability to monitor, document and notify police of gunfire that often goes unreported is comforting and a reassurance that they are not being ignored by local police departments.

Conversely, a segment of citizens see the technology as invasive. In the wake of incidents where voices were captured in the moments following a shot and used as evidence in court, concerns that the technology could be used to violate Fourth Amendment rights of people not involved in crimes have become an issue.

Analyzing Cost and Viability

While some agencies welcome this technology, others are hesitant. In cities like Dallas, Texas, and Baltimore, Maryland, the price tag has hindered proposals to install gunfire detection systems.

At a price of $60,000 to $90,000 per square mile, depending on terrain and the number of sensors deployed, it’s not hard to see why some cities have concerns, though some law enforcement agencies use federal grants to offset the cost.

In addition to funding, mounting sensors on private property can also present hurdles for cities.

Despite the financial, property and privacy issues, the trend of implementing this technology continues to grow. Hartford City Councilman Kyle Anderson echoed a popular sentiment in 2013 as his Connecticut city weighed its options going forward with SST at a cost of $75,000 per year.

“The money spent concerns me, but not to the point I want to pull the plug,” Anderson said in an interview with Fox CT. “If we get one person convicted of murder because of it, isn’t it worth what we paid for it?”

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