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More Information about SST and ShotSpotter can be found
. The National Gunfire Index
eBooks can be downloaded at www.ShotSpotter.com/ngi. You can also follow SST and
ShotSpotter solutions on Twitter
All rights reserved. ShotSpotter® Flex℠, ShotSpotter® SiteSecure™,
ShotSpotter®, SST™ SecureCampus, and the ShotSpotter logo are registered
SST, Inc.™, SST and ShotSpotter technology are protected by one or more issued
U.S. and foreign patents, with other domestic and foreign patents pending,
as detailed at www.ShotSpotter.com/patents
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.
Several police tools and technologies capture information that is already in public
view: license plate readers, video cameras at stoplights and ATMs, combined
video/audio surveillance cameras, facial recognition algorithms, etc. Unlike general
audio and video surveillance devices, such as the tens of thousands of video cameras
deployed in our nation’s cities which monitor general activities, gunshot detection
technology is designed to trigger on loud explosive or impulsive sounds that may
likely be gunfire and occur only rarely—and that the public already “hears”.
Although courts have held that individuals speaking in a manner which can be
overheard on public streets do not have the expectation of privacy which would
trigger federal wiretapping laws, SST wants to provide stronger protection of
individual rights to privacy than is strictly provided for by law. As a result, we
law requirements and to protect individual privacy.
Please note: this section refers to the SST ShotSpotter outdoor gunfire detection
technology. Indoor sensors are entirely different and provide additional privacy
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
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.
tighten the parameters for audio availability: the permitted audio length is
strictly limited to two seconds before and four seconds after. Unless someone is
yelling loudly enough to be heard in public, and also doing so within two seconds
before or four seconds after a loud, explosive acoustic incident, the audio will be
flushed from the sensor’s buffer and overwritten. The simple fact is that there has
never been a case of a private conversation overheard or monitored by any
ShotSpotter sensor anywhere at any time. Period.
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 2015 analysis in this report is based on 62 communities that had Shotspotter
Flex coverage (reviewed alerts) and were collecting data as of December 31,
3. In order to perform an apples-to-apples comparison of gunfire rates per square
mile for 2014 and 2015, only those 46 communities that had Flex coverage for more
than 4/5 of the non-holiday portion of the year in both 2014 and 2015 are used in
4. Some communities were not covered during some parts of 2014 or 2015. 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 calculate the number of incidents by day and
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
5. 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
Incidents during the holiday periods of New Years and 4th of July are not counted in
the statistics unless explicitly noted because of the prevalence of celebratory
gunfire during those holiday periods and the fact that it is highly inconsistent
with the normal
patterns. The holiday periods are from December 30, 2013 to January 2, 2014,
December 30, 2014 to January 2, 2015, June 27 to July 9, 2014, and June 12 to
July 12, 2015.
6. Communities without at least 20 incidents in all of 2014 were not used when
comparing gunfire rates.
7. 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
previously. Incidents were counted as gunfire if they were classified as Single
Gunshot, Multiple Gunshot, or Possible Gunfire by SST-certified review personnel.
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.
8. 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. If the polygon coordinates are not available, the contracted area is used. 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.
9. When the Friday, Saturday and Sunday gunfire totals are compared to the rest 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
10. Individual hours of the week and days of the week were calculated on a local
ShotSpotter Gunfire Index Release – 2016
NEW HAVEN, ATLANTIC CITY AND SAN FRANCISCO AMONG TOP FIVE U.S. CITIES WITH HIGHEST DECLINE
IN GUNFIRE FROM 2014 TO 2015 ACCORDING TO SST NATIONAL GUNFIRE INDEX
Northeast Tops the Nation with Biggest Decrease in Gunfire (-27.1%), Followed by the West (-22%)
NEWARK, California – February 26, 2016 –
Gunfire incidents declined by a median of 12.8% in 2015 in key U.S. cities across
the country—particularly in the northeast and west—according to the National Gunfire
Index released today by SST, Inc. the global leader in gunfire detection and
location technology. Among U.S. cities using SST’s ShotSpotter technology, three of
the top five with the largest reduction in gunfire incidents from 2014 to 2015 were:
New Haven, CT (- 38.5%), Atlantic City, NJ (- 35.3%), and San Francisco, CA (-
34.6%). Overall, the cities in the Northeast region saw a 27.1% decline and those in
the West experienced a 22.0% drop in gunfire incidents over the same time
The annual ShotSpotter 2015 National Gunfire Index is based on data from a
statistical sample of U.S. cities using ShotSpotter that had full year deployments
in both 2014 and 2015. The year-over-year comparisons of 46 cities had a total
coverage of 172.9 square miles and a median coverage area of 3.1 square miles. The
median reduction in the rate of gunfire incidents in those cities was 12.8%. 36 of
the 46 cities saw a decline with a median decrease of 20.1%.
SST’s National Gunfire Index delivers objective urban gunfire incident data that
clearly demonstrates that gun violence in the U.S. is much greater than that which
is typically measured in terms of homicides and non-fatal shootings alone.
• Total number of gunfire incidents in 2015 National Gunfire Index is 54,699.
• December 25, Christmas Day, was the most intense single day of gunfire incidents
(excluding New Years Eve and Fourth of July) in 2015 with 266 incidents
• The single busiest hour for gunfire activity during 2015 was Sunday, November 1
between 11:00 PM and midnight, when Kansas City, Missouri had 24 gunfire incidents.
• The most active day and hour of the week for all cities during 2015 was Saturday
at 2:00 am.
• The highest rate of gunfire is in the Midwest with an average of 351.9 gunfire
incidents per square mile during 2015 with the lowest rate in the Northeast with
73.7 incidents per square mile.
• Rounds per incident were up in all regions from a median of 3.5 in 2014 to 3.8 in
• In 2015, 29% of cities experienced five or more rounds of gunfire per incident,
and 10% logged nine or more rounds per incident.
• There were 144.7 incidents per square mile in 2014 compared with 123.2 incidents
per square mile in 2015.
• The top five cities with a decline in the 2015 National Gunfire Index also include
New York cities Huntington Station (- 50.2%) and Brentwood (- 37.4%).
In the ten cities that saw an increase, three of those cities had slight increases
of less than 2.5%; four cities experienced a “dead cat bounce” increase (where they
saw significant decreases in the previous year’s gunfire index and this year saw an
increase although still below their 2013 levels) and the remaining three cities saw
increases which can be attributed to an uptick in local crime and in one case the
non use of ShotSpotter.
“ShotSpotter is a proven gun violence detection tool as well as an objective
thermometer measuring the inconvenient truth of urban gunfire in cities across the
United States, from New York City to Sacramento. Our unique platform allows us to
track the positive outcomes cities experience when leveraging ShotSpotter as part of
a comprehensive gun violence abatement strategy,” said SST President and CEO Ralph
A. Clark. “We believe this data can be constructive in not only shaping policy
conversations, but also demonstrating what can be accomplished when law enforcement
combines people; process and technology to better connect to and protect those
communities challenged with gun violence.”
“In San Francisco our focus has been on reducing gun violence and it appears that
our efforts and community partnerships are having the desired effect,” said San
Francisco Police Chief Suhr. “While there is no level of gun violence that is
acceptable; with that said, we are headed in the right direction and we credit
ShotSpotter with helping us achieve this.”
“We are tremendous believers in the ShotSpotter technology and look forward to
expanding its use across New Haven,” said New Haven Mayor Toni N. Harp. “From 2011
to 2015, homicides are down 55 percent and non-fatal shootings are down 52 percent.
When we first started using ShotSpotter we would never have imagined numbers like
these, and while there are many reasons for these positive trends, ShotSpotter is an
important part of the overall approach, enabling us to apply breakthrough technology
to try and save lives and reduce crime in New Haven.”
“With ShotSpotter technology, our officers now respond faster to the scene and have
been able to find victims and evidence quickly. ShotSpotter is also an important
tool that helps with improved community action and engagement, and all of this has
helped us to achieve a 35.4 percent decrease in gunfire violence from 2014 to 2015
across the city,” said Atlantic City Police Chief Henry White. “Our goal is to do
everything we can to catch the people who commit gun violence, and ShotSpotter is
helping us do that.”
ShotSpotter® Flex℠ helps local law enforcement agencies detect gunfire accurately,
protect officers with increased tactical awareness, and connect the police to the
community while also connecting police to their mission to serve and protect. With
the precise location of illegal gunfire incidents, first responders can more quickly
aid victims, collect evidence, and identify, investigate and ultimately apprehend
armed, dangerous serial shooters.
ABOUT SST, INC.
SST, Inc. is the global leader in gunfire detection technology, providing the most
trusted, scalable and reliable gunfire alert and analysis solutions available today.
SST’s ShotSpotter Flex™ is the leading gunfire alert and analysis solution for
detecting gunshots and providing critical intelligence to give law enforcement
agencies the detailed real-time data needed to investigate, analyze and prosecute
gun related crimes. SST’s ShotSpotter SiteSecure provides critical indoor/outdoor
infrastructure protection against active shooter attacks. The company’s deep domain
experience of twenty years, intellectual property including 33 issued patents, along
with cumulative agency best practice experience, enables measurable outcomes that
contribute to reducing gun violence. SST is a proven solution provider with more
than 90 installations across the United States and the world. Privately held, the
company’s collective inspiration is sourced from our founder’s core belief that the
highest and best use of technology is when it can serve a public good. Details can
be found at www.ShotSpotter.com
. Details about our U.S.
and foreign patents can be found at www.ShotSpotter.com/patents
More Information about SST and ShotSpotter can be found at www.SST-Inc.com
. The National Gunfire Index
eBooks can be downloaded at www.ShotSpotter.com/ngi. You can also follow SST and
ShotSpotter solutions on Twitter
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Liz Einbinder +1 (415)