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Acoustic Surveillance Systems

A 17-year-old Beloit, WI girl sustained a life-threatening gunshot wound at the hands of an unknown gunman. The Beloit Police Department’s ShotSpotter Gunshot Location System® detected and located the incident in real time. As a result, patrol units and EMS were dispatched to the scene almost two minutes before (yes, before) the first call to 9-1-1. By alerting Beloit officers to the shooting and providing them with the victim’s exact location, the technology helped them react faster and respond with emergency medical treatment, ultimately assisting in saving her life.

Similar scenes in which the ShotSpotter GLS has helped police render life-preserving aid have played out over 220 times since 2005, and the rate is rapidly increasing. In the first six months of 2009 there were 57 such cases—an average of two per week. This is the “expected” benefit of gunshot location technology because it’s the most obvious. But it isn’t the only benefit.

Adoption of gunshot location technology has recently increased rapidly. In 2004, only five cities had deployed ShotSpotter. By mid-2009, that number had grown to 45. Coverage areas have also expanded, from two square miles in 2004 to as many as 17 square miles in 2009. Strong community support, particularly from community safety partnerships and other civically-oriented organizations, has fueled adoption. With such broad-based support, it might be surprising that there remain “unexpected” benefits to gunshot location technology, but several exist.

Immediate Notification

When cities first deploy gunshot location technology, their initial thoughts naturally focus on the “immediate notification” value of gunshot location. This is to be expected. Depending on the city, 9-1-1 reporting rates for gunfire can range anywhere from 20% (commonly) to 70% (rarely). The average is below 50% in cities deploying ShotSpotter.

By deploying technology with a proven track record of increasing police notification to 80% or higher, regardless of underlying reporting rate, cities get more timely and much more accurate information about the location of gunfire. That translates into arrests made, weapons seized, lives saved and increased community confidence.

So it is natural for the most obvious and most talked about value of gunshot location technology to be a higher, faster and more accurate reporting rate. After all, the results are immediately obvious: within days, sometimes within hours, police make arrests, such as the seizure of an illegal AK-47 on the streets of Richmond, CA, this past May that occurred within hours of commissioning the city’s ShotSpotter GLS.

Situational Awareness Increases Officer Safety

The ShotSpotter GLS records audio from each shooting incident as it is heard at each sensor. It reports incidents both to dispatch and to in-car mobile data computers (and in some cities, also to police helicopters). One perhaps unexpected benefit is that officers gain critical situational awareness as they drive to the scene, both by knowing the precise location (e.g., “10 feet behind the garage, to the left of the property line”) and by listening to the incident (e.g., “it sounds like two guns; one is clearly a large caliber”).

Because they are often arriving on scene before 9-1-1 calls come in, officers could potentially be driving into the middle of a gunfight. The combination of subsequent incident notifications (in other words, of continued gunfire in the same location) and the actual audio of each shooting (in which officers can identify, for example, fully automatic weapons or multiple shooters, thus requiring different tactics and procedures) has helped officers arrive fully prepared to handle a developing situation.

Take the example in which four separate shooting incidents, with a total of at least six shooters, took place within one minute and 52 seconds. Before they arrived, officers knew they would need a large response force in order to take decisive control of the situation and thus avoided being outnumbered and potentially ending up in harm’s way themselves.

As with so many other data-driven processes, there are substantial cost benefits to this approach. By having a confirmed location and details on incident severity, the appropriate quantity of responders is deployed in a tactically sound manner using the closest available responders. A department thereby saves time and frees up resources for other activities, thus reducing overtime, which is the single biggest variable expense in many departments.

Better Intelligence Drives Crime Reduction

ShotSpotter produces and permanently stores the precise geolocations (latitude/longitude data) for each incident, along with the number of rounds fired, the speed and direction of moving shooters and in some cases the number of shooters involved; the ShotSpotter GLS repository becomes the de facto “gunfire history” of the city. This is clearly a benefit because it contains data never reported to 9-1-1 and therefore has a noticeably different pattern than 9-1-1 and CAD data.

Customers notice a distinct 9-1-1 under-reporting phenomenon in neighborhoods in which gunfire is prevalent and experience an over-reporting phenomenon in neighborhoods in which gunfire is less common. Even in areas where crime rates are high, most gun-related homicides are eventually reported to 9-1-1, and the data tend to skew towards the reporting of gunfire used in the commission of a homicide, leaving out gunfire from, for example, the test firing of those weapons several blocks away in advance of committing a crime.

By contrast, customers comparing 9-1-1 data to ShotSpotter data often note an increasing gunfire rate—especially gunfire not (yet) related to homicidal activity—early enough to stem violence. This is intelligence-led policing at work.

Take the case of Rochester, NY, which has used ShotSpotter data to enforce a “zero tolerance” policy on all weapons discharges. Armed with ShotSpotter data, the department has applied intelligence-led policing techniques to crack down on crime—often before violence escalates into homicides. Christopher Delaney of the Rochester Police Department commented that prior “to the capture of overall gunfire activity and knowing the exact location of where gunfire occurred, we did not have the clues to infer potential future shootings.”

Take another example in which a crime hotspot was “hidden” by low 9-1-1 reporting rates—until ShotSpotter data was overlaid. In one region, three homicides were located and each reported to 9-1-1 within a single month. Compared to the rest of the area, three gunfire incidents is not substantially more than occurs elsewhere. But when the ShotSpotter data was incorporated, another 11 shootings (roughly one every other day) showed up in this one area. The hotspot was revealed.

Using this otherwise unavailable intelligence, law enforcement focused its existing resources in the area. The results were immediate: in the month subsequent, not a single shooting occurred. The area saw a total of 14 incidents in over 15 months thereafter.

Measuring and documenting real-time crime intelligence allows departments to do better planning. By properly staffing shifts, attacking hotspots and measuring results, departments can both manage their personnel costs more effectively and actually show concrete data in support of compelling grant requests that can offset budget deficits.

Over time, grant funds that are spent on measurable crime reduction activities are more likely to receive continued funding. As a result, several departments using the ShotSpotter GLS have successfully sought repeated follow-on grants supported by initial results to expand their use of this technology throughout their cities.

Reduced Investigations and Increased Convictions

Although cities like Los Angeles have seen homicide reduction rates of 40% in areas where the ShotSpotter GLS is in use, homicides will still occur regardless of how good a department’s intelligence is. When they do, another aspect of this technology becomes critical to more efficient and successful investigations and prosecutions. Because the ShotSpotter GLS records incidents audio time-stamped with GPS (atomic clock) time from all reporting sensors, and because it detects and separately locates each individual round fired, ShotSpotter data can provide evidence that helps put criminals away for a long time.

It therefore also has a history of convincing defendants to plead guilty instead of facing the specter of a jury hearing ShotSpotter-provided audio and details during trial.

Take, for example, a homicide committed by two gang members in South Los Angeles, CA. The ShotSpotter GLS located the incident in real time, but the victim managed to stagger away from the scene and died sufficiently far away that responding officers did not see him when they responded to the scene.

The sole eyewitness was murdered prior to trial. The prosecution wished to prove that the assailants fired their weapons almost simultaneously, and therefore that they were both guilty of first degree murder. Without the now-deceased witness, that was a tall order. “The ShotSpotter GLS . . . was able to show that two different weapons were being fired, as well as the sequence in which those weapons, Weapon A and Weapon B, were fired,” said Los Angeles County Sheriff’s Detective Ty Labbe.

“It was also able to show distance, which put Shooter A and Shooter B where the witness said they were standing in relation to the victim. These distance measurements corroborated the location where the physical evidence (shell casings) was located by investigators, giving us evidence to recreate the crime scene and further corroborating the testimony of the lone witness to the murder.”

The evidence did the trick. Deputy District Attorney Gutierrez played the ShotSpotter-recorded audio to the jury: “When the sound of the gunshots was played, the jurors realized ‘we are hearing the shots fired at this person who ultimately died.’” Both defendants were convicted of first degree murder.

While the cost to prosecute violent crime cases varies by location, some users of gunshot location technology report that investigating and prosecuting a single homicide can cost as much as $1 million. By directing investigators to evidence that can be tied to an event (such as a precise timeline, sequence of events or even physical evidence at the scene) and then producing this information, including the actual audio of a violent crime, as evidence before trial, defendants often heed the advice of counsel to take a “deal” from the prosecutors, lest they face such strong evidence at trial. It’s no wonder, then, that some departments report cost reductions as high as 50% in ShotSpotter-assisted cases.

These unexpected benefits deliver value far beyond immediate notification to cities deploying gunshot location technology. Improving officer safety, augmenting and clarifying gunfire intelligence, and speeding investigation and prosecution are results which might explain why there has been such an explosion in the adoption of gunshot location technology over the past several years. Of course, the 220 shooting victims whom officers have reached in time to provide potentially life-saving aid have their own voices; they are among several voices asserting the benefits of gunshot location technology.

James G. Beldock is the President & CEO of ShotSpotter. He maintains a blog at

Published in Law and Order, Oct 2009

Rating : Not Yet Rated

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