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Leveraging Technology to produce Societal Benefits
As technology continues to advance, balancing its benefits against some of its inherent risks to privacy continues to be an issue which confronts us all. What’s true for technology in general is also the case in the realm of public safety. Technological advances have provided significant benefits to those tasked with keeping us safe while at the same time raising appropriate dialogue about how we can leverage those benefits while minimizing unwarranted intrusions on personal privacy.
Please note: this section refers to the SST ShotSpotter outdoor gunfire detection technology. Indoor sensors are entirely different and provide additional privacy protections.
ShotSpotter sensors are specifically designed to be triggered by loud explosive or “impulsive” sounds only. The entire system is intentionally designed not to permit “live listening” of any sort. Human voices do not trigger ShotSpotter sensors. There are many other loud noises that do not trigger ShotSpotter: car doors slamming, people yelling “bang bang!”, loud music, airplane engines, leaf blowers, cheering, highway noise, car engines revving, drag races or tires squealing.
In addition, sensors are intentionally deployed in elevated locations (typically 50-100 feet above street level on building rooftops, sometimes 30-40 feet above ground on a street pole) for three reasons:
1) to maximize their ability to “listen to the horizon” and thereby reduce the number of sensors required;
2) to minimize the background noise from cars and other street noises, thus also reducing the number of sensors required; and
3) to minimize the chance that a human voice will be intelligible, however briefly, in order to protect privacy.
ShotSpotter sensors do not use “high gain,” directional, or other specialized microphones.
The microphones themselves are similar to those in a mobile phone. When spoken outdoors at distances in excess of approximately 10 feet, a private conversation spoken in a normal voice is simply not intelligible to a human, to a mobile phone, or to ShotSpotter sensors. This is an intentional engineering and design choice made to ensure that ShotSpotter sensors cannot be used to monitor private conversations. It would be safe to say that an individual walking down the street and speaking into a mobile phone is more likely to unintentionally overhear and transmit the private conversation of someone else walking and talking nearby than that a ShotSpotter sensor, far further away, and only triggered by loud, impulsive noises, would be.
When a loud explosive noise triggers a sensor, it instantly sends summary data about the acoustic event (e.g. time stamp, sensor location, amplitude and envelope characteristics, etc. but explicitly not the audio of the sound itself) to a centralized processor at our SST-operated data center. There, if no other sensors trigger (i.e., if only one sensor hears the particular impulse), nothing else happens and no incident is created. If multiple sensors (usually 3 or more) report impulsive noises within a narrow time window which are sufficiently loud and mathematically consistent with their having originated at a single location, software algorithms attempt to calculate that origin location. If an accurate location can be determined, the associated sensors’ data are aggregated (again, without the audio) and an incident is “created” in a centralized database. A second filter then applies artificial intelligence and statistical techniques to attempt to identify what type of sound originated at this location based on the measurements of the sound. In most cases, the parameters of the sound permit the incident to be filtered out, because it is, e.g., a pile driver or a jackhammer. In a percentage of cases, the characteristics of the sound are consistent with an explosion (gunfire, firework mortar, firecracker, backfire, etc.). In those cases, and only in those cases, the sensors are permitted to push a small snippet of audio to our data center. Otherwise, the audio will be flushed from the sensor’s buffer and lost permanently. This is an intentional privacy-driven design: an active step must be taken only in the context of an explosive triggering acoustic event, or the audio is erased and overwritten.
In those cases in which an explosive triggering acoustic event is detected and located, the brief audio snippets are sent to SST’s Real Time Incident Review Center (IRC) for analysis and alert qualification by highly trained experts in gunshot acoustics. Within seconds, SST’s IRC sends those qualified gunfire alerts directly to a dispatch center, PSAP, patrol officers or other agencies for an effective, coordinated response. The gunfire alerts that the ShotSpotter system delivers to our police agency clients provide a digital record of violent gun crimes in progress, including minimally brief snippets of audio recordings of those crimes. For any given illegal gunfire incident, that snippet can only contain a few seconds of audio before the first shot and after the last shot. The purpose of these short seconds of audio on either end of the gunshots is to allow a human reviewing in the incident to clearly tell when the shooting starts and stops, including judges and juries during possible future criminal proceedings.
No Live Audio Streaming
As mentioned above, the entire system is intentionally designed not to allow “live listening” of any sort. There is no “listen” button available to law enforcement, or to the staff of our Incident Review Center, except the buttons which replay the specific few seconds of incident audio surrounding an impulse noise determined to likely have originated from an explosive source.
No Private Conversations
ShotSpotter sensors do not have the ability to listen to indoor conversations. They do not have the ability to overhear normal speech or conversations on public streets. Recently, privacy zealots have pointed to three extremely rare “edge cases” (3 out of approximately 3 million incidents detected in the past 10 years), in which a human voice yelling loudly in a public street at the scene of a gunfire incident was overheard for a very brief period (a few seconds). They have inaccurately assumed that ShotSpotter sensors are constantly transmitting audio streams, or somehow have been reconfigured to listen to private conversations. That simply isn’t true. In one of these three cases, only two words were overheard; in the others, a sentence was heard before the gunshot and in the other a similar number of words were heard immediately after a gun shot. In all cases, the words were yelled loudly, in a public place, at the scene of a gunfire-related crime, and within a few seconds of that event.
Policy and Security Minutiae
If you are still with us, here are some additional details: All servers and software used to process, store and protect data are managed and maintained by SST. Police agencies subscribe to the hosted service on an annual basis, radically streamlining the cost and complexity of using gunfire alert and analysis to enhance awareness, response and community safety. SST owns these data and does not release to anyone other than the customers under contract and according to the terms of that contract, thus further ensuring the safety and security of the data. Customers do not have administrative access to our servers, software, sensors, or any other means to circumvent SST’s security and privacy measures.
SST has taken appropriate security approaches to prevent anyone or any entity from gaining unauthorized access to our systems including our processors, networks or sensors. In addition to the fact that the system is designed not to permit live streaming audio, even if an intruder were to take control of our data center and network, they could not “make” a sensor deployed in the field stream audio. It simply isn’t possible: the sensors operate on a proprietary protocol and intentionally do not contain code which permits them to stream audio. Asymmetric key encryption is used to control access to sensors, and SST employees are required to use dual-factor authentication to gain access to most critical systems.
In the event that the ShotSpotter system fails to detect an incident, it is SST’s policy only to respond to requests for incident data or audio related to specific, verified gunfire incidents. In no event does incident audio extend beyond 2 seconds before and 4 seconds after an incident.
In addition to all of these technical and security measures taken to protect privacy and prevent misuse, SST has adopted a human resources policy to ensure that employees and contractors adhere to our privacy policies.
In the end, we believe that the privacy of our citizens and the community and social benefits of decreased gun violence are not at odds with each other. Our ultimate goal is to ensure that both are satisfied. We believe we have taken all reasonable and necessary precautions to assure a robust and strong privacy posture. We will continue to review, revise—and strengthen if necessary—these policies.
Methodology and Notes
1. The data in this Index is taken only from the areas covered by Shotspotter systems. There is no assurance that conclusions drawn from this data will be valid outside the coverage areas.
2. The 2017 analysis in this report is based on 87 communities that had Shotspotter Flex coverage (reviewed alerts) and were collecting data as of December 31, 2017. Of these, 69 were used in providing data for 2017 gunfire, and 58 were used in comparing 2016 to 2017.
3. Only incidents within our coverage areas were counted in gunfire rate per square mile calculations.
4. To be counted in the 2017 gunfire rate calculations, a community had to have Flex coverage for more than 4/5 of the non-holiday portion of 2017.
5. In order to perform an apples-to-apples comparison of gunfire rates per square mile for 2016 and 2017, only those 58 communities that had Flex coverage for more than 4/5 of the non-holiday portion of the year in both 2016 and 2017 are used in the comparison. Furthermore, only those incidents within the coverages areas as of the beginning of 2016 were used in comparing gunfire rates for 2016 vs. 2017. Any coverage areas and incidents in those areas that were added after the beginning of 2016 were ignored in the comparison. However, the added coverage areas were included for the analysis of 2017-only data.
6. Some communities were not covered during some parts of 2016 or 2017. This could occur due to power outages (as from hurricanes), coverage had not started, etc. Therefore, when calculating values such as gunfire incidents per square mile, care must be taken to account for the different number of days of coverage for different communities. The chosen solution was to impute the number of gunfire incidents for those days for which there was no coverage, taking into account known information about incident rates for the community, the day of the year, the day of the week, and the year. This method is like proration, but is more accurate. Imputation of incident data for a year is done only for communities that have coverage data for more than 4/5 of the non-holiday portion of that year.
This method was cross-checked using cities with two full years of data, comparing actual data to imputed values for simulated missing values. The average difference by city between the gunfire rates using imputed values vs. using actual values was only 2.2%, showing that imputation can be relied on to give accurate results.
7. Gunfire incidents for a year period were counted if the local time in the time zone of their occurrence was between 00:00:00 standard time (i.e., midnight) on January 1 and 23:59:59 on December 31st (i.e., 1 second before midnight on January 1).
8. Incidents during the holiday periods of New Years and 4th of July are not counted in the statistics for any city unless explicitly noted because of the prevalence of celebratory gunfire and fireworks during those holiday periods and the fact that they are highly inconsistent with the normal patterns. The holiday periods are January 1 through January 3, 2016; June 19, 2016; June 24, 2016 through July 14, 2016; December 31, 2016 through January 1, 2017; June 27, 2017 through July 9, 2017.
In addition, some cities had other days near the holiday periods with exceptionally large volumes of celebratory gunfire and fireworks. The gunfire data for these days were not used, but were filled in by imputation. The total number of these days is very small.
9. Cities in the Caribbean and Puerto Rico are not counted in gunfire rate calculations or comparisons because of long-term power outages at the end of 2017 caused by Hurricane Maria. Data from these cities are counted in other calculations, such as the number of rounds per incident, percent gunfire by hour of day, etc.
10. Communities without at least 20 incidents in all of 2016 were not used when comparing gunfire rates.
11. Incidents were counted only after formal qualification and operational use of ShotSpotter data by the client agency began, even if gunfire or other incidents were detected previously. Incidents were counted as gunfire if they were classified as Single Gunshot, Multiple Gunshot, or Possible Gunfire by SST-certified review personnel. All other incident types (fireworks, firecrackers, explosions unrelated to gunfire, transformer explosions, thunder, lightning, helicopters, etc.) were excluded from all statistics presented in this report. Gunfire incidents not reviewed by SST-certified review personnel are also excluded.
ShotSpotter data does not remain static, as information and adjustments are often made several days or weeks after initial detection (as forensic evidence is analyzed, cases are investigated, etc.). This report takes into account the most accurate and recently-available information.
12. Square mileage is measured on the basis of contractual coverage area. For each such area, the geographic area is defined as a polygon surrounding each coverage area. In some cases, small areas within these coverage areas are intentionally excluded when gunfire is regularly expected in those specific locations (e.g. a legal outdoor shooting range or police practice range). In those cases, gunfire which takes place in those locations outside of authorized areas is still included in the tallies, but gunfire which takes place during permitted (expected) periods is not included.
13. When the gunfire totals are compared for days of the week, a day is defined as starting at 06:00:00 local time and extending to 05:59:59 the next morning. For example, early 02:05 Sunday morning is counted as Saturday night.
14. Individual hours of the week and days of the week were calculated on a local time basis.
ShotSpotter Gunfire Index Release – 2017
SHOTSPOTTER DETECTED OVER 86,000 GUNFIRE INCIDENTS ACROSS THE UNITED STATES IN 2017
ShotSpotter National Gunfire Index (NGI) is the most comprehensive study to capture, analyze, and report on gunfire incidents annually
NEWARK, Calif. – April 3, 2018
– ShotSpotter (Nasdaq: SSTI), the leader in gunshot detection solutions that help law enforcement officers and security personnel identify, locate and deter gun violence, today announced results of their annual ShotSpotter National Gunfire Index (NGI) report, a gunfire incident report based on 87 U.S. cities using ShotSpotter technology during 2017.
Many medium and large-sized cities where ShotSpotter is deployed across the U.S. saw a measurable reduction in gunfire ranging from 6 to 34 percent for 2017 vs 2016, including: (in alphabetical order) Denver, CO; Minneapolis, MN; Pittsburgh, PA; Riviera Beach, FL; San Francisco, CA; Savannah, GA; Washington D.C., and Worcester, MA.
The ShotSpotter 2017 National Gunfire Index report is based on data from U.S. cities that used ShotSpotter during the same time period year-over-year in 2016 and 2017. Overall, the western region of the U.S. saw the most significant decrease in gunfire activity. The single busiest day of reported gunfire was June 22, 2017 in a midwest city with 75 incidents – down significantly from the busiest day of gunfire in 2016 that topped out with 339 incidents on October 23, 2016. The ShotSpotter National Gunfire Index found the busiest hour for gunfire in 2017 for any one city was on November 6 from 8:00 pm to 9:00 pm, with 35 gunfire incidents.
The ShotSpotter National Gunfire Index also revealed that incidents with single rounds were on the rise during 2017 and a trend towards a longer “weekend” with increased activity on Mondays, as well as the traditional spike in gunfire seen during the period of Friday, Saturday and Sunday.
Other key findings include:
Gunfire by night of the week – a longer “weekend” period emerges
• The total number of incidents per day reported by ShotSpotter rose 10% on Monday compared to 2% Tuesday through Friday.
• Monday edged out Thursday to become the fourth busiest night after (in order of total gunfire incidents reported) Saturday, Friday, and Sunday
Average number of rounds per reported incident was mostly steady, except for the West and Caribbean* where total incidents remain the highest, but dropped considerably year over year.
• Northeast 3.3 rounds per incident (2016, 3.3)
• Midwest 3.5 rounds per incident (2016, 3.6)
• South 3.7 rounds per incident (2016, 3.7)
• West 3.9 rounds per incident (2016, 4.4)
• Caribbean (Puerto Rico and U.S. Virgin Islands) 4.7 rounds per incident (2016, 6.3) *
*Cities in the Caribbean and Puerto Rico are not counted in gunfire rate calculations or comparisons because of long-term power outages at the end of 2017 caused by Hurricane Maria. Data from these cities are counted in other calculations, such as the number of rounds per incident, percent gunfire by hour of day, etc., and is derived from the coverage period of January 1 to September 5, 2017.
Rate of gunfire incidents by region – when looking at gunfire incidents by geographic region, the Northeast has the lowest number of gunfire and the Midwest has the highest number of gunfire incidents.
Gunfire incidents peak between 10PM-12 midnight – the number of gunfire incidents by hour of day peaks at 10PM-11PM followed by 11PM-12 midnight and starts declining at midnight. The lowest number of gunfire incident hours are generally the 6AM-10AM range.
“ShotSpotter has proven to be a valuable tool to help improve our performance in reducing gun violence,” said Worcester, MA, Police Chief Steven M. Sargent. “Our officers depend on ShotSpotter to manage resources, identify patterns of crime and thoroughly investigate each shooting incident. As a result, we have seen measurable results and Worcester remains one of the safest cities of its size in the northeast.”
“Our annual ShotSpotter gunfire index provides important data that shines a light on gun violence trends that can empower law enforcement to make strategic decisions based on that knowledge,” said ShotSpotter President and CEO Ralph Clark. “While there is still much to be done to make our cities safer, by working closely with law enforcement across the country we are seeing large reductions in gunfire as the combination of technology, community engagement and new policing practices make a positive impact.”
ShotSpotter, is used in more than 87 cities across the country to help law enforcement agencies reduce gun violence. Through its acoustic sensing capability and enterprise-grade software, ShotSpotter can detect and locate gunfire in near real time. Alerts are then broadcast to 911 dispatch centers, patrol cars and even smartphones, with the location, number of rounds fired, and approximate number of shooters, to law enforcement and public safety officials. These alerts help enable first responders to get to the gunfire location quickly and aid victims, collect evidence and apprehend offenders.
ABOUT ShotSpotter, Inc.
ShotSpotter is the leader in gunshot detection solutions that help law enforcement officers and security personnel identify, locate and deter gun violence. ShotSpotter is based in Newark, California and offers its solutions on a SaaS-based subscription model.
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