U.S. Department of Justice

Office of Justice Programs

National Institute of Justice

R e s e a r c h i n B r i e f

National Institute of Justice

Jeremy Travis, Director

continued...

Random Gunfire Problems and

Gunshot Detection Systems

by Lorraine Green Mazerolle, Cory Watkins, Dennis Rogan, and James Frank

December 1999

What is known about

random gunfire problems

Random gunfire problems are distinguishable from other types of shooting

incidents such as urban sniper attacks,

gang shootouts, domestic homicides, and

revenge shootings because (1) random

gunfire is strictly an outdoor activity;

(2) it is not usually part of other criminal

activity such as drug dealing, assaults,

or robberies; and (3) random gunfire

shooters do not fire their weapons to

intentionally injure or kill people.

In many U.S. urban areas, random gunfire

is considered a problem, typically involving people drinking alcohol and watching

televised sporting events and then walking outside to fire their weapons into the

air in celebration. People also tend to

fire their weapons on New Year’s Eve,

Cinco de Mayo, Fourth of July, and other

significant holidays. Police report that

random gunfire shooters believe their

actions are harmless. Shooters state that

firing their weapons in the air does not

endanger lives or damage property.4

Policymakers, police department personnel, city prosecutors, and community

residents across the United States have

implemented a variety of initiatives to

control serious shooting and other gunrelated problems.5

 Yet only a few local

governments have developed programs

Random gunfire is a significant problem in many large cities throughout the

United States.1

 Random gunfire has been

defined as “the indiscriminate discharge

of firearms into the air,” which generally

occurs during the celebration of holidays,

during weekends or sporting events, and

often in the context of drinking.2

Communities across the United States

have instituted a variety of efforts to reduce random gunfire problems, including

public awareness campaigns and the use

of technological devices to detect and

alert the police to incidents of gunshots

and explosions. Generically known as

“gunshot detection systems,” the technology includes an acoustic sensing system

capable of identifying, discriminating,

and reporting gunshots to the police

within seconds of a shot being fired.3

This Research in Brief summarizes the

findings of field studies of two gunshot

detection systems: Trilon Technology’s

ShotSpotterTM system, which has operated in Redwood City, California, since

early 1996, and Alliant Techsystems

Inc.’s SECURESTM system, installed

for 2 months in 1996 in a neighborhood

with high levels of random gunfire in

Dallas, Texas. This Research in Brief

also outlines how the police used the

gunshot detection system in Dallas and

what officers working in the test sites

think of the technology.

Issues and Findings

Discussed in this Brief: The findings of two field studies of acoustic

sensing systems designed to detect

the sound of a muzzle blast from a

gun and, within seconds of the shot

being fired, triangulate within some

margin of error the location from

which the shot was fired, before

alerting the police about the gunshot. The research team examined

the effectiveness of Trilon Technology’s ShotSpotterTM system,

which the local police department

has operated in Redwood City,

California, since early 1996, and

the Alliant Techsystems Inc.’s

SECURESTM system, which police installed for 2 months in a neighborhood with high levels of random

gunfire in Dallas, Texas, in 1996.

This Research in Brief also outlines

how the police used the technology

in Dallas and what officers working

in the study sites think of gunshot

detection systems.

Key issues: Anecdotal evidence

from the media and interviews with

local officials, police, and community members suggests that random

gunfire is considered a serious

problem in many large cities in the

United States. Random gunfire has

been defined as “the indiscriminate

discharge of firearms into the air,”

which generally occurs during holiday celebrations, during weekends

or sporting events, and often in the

context of drinking.

Random gunfire problems are

distinguishable from other types of

shooting incidents such as urban

sniper attacks, gang shootouts,

domestic homicides, and revenge

shootings because (1) random
2

R e s e a r c h i n B r i e f

injuries. The statistics also fail to differentiate between random gunfire and

other criminal incidents when shots are

fired, such as drive-by shootings, revenge

shootings, shootings during drug transactions, and so forth. As such, there is very

little systematic information about the

extent, environmental causes, social

context, and societal costs of the random

gunfire problem.

The study neighborhood

The Dallas study began with a systematic

analysis of the random gunfire problem

in that city’s Oakcliff neighborhood. Researchers reviewed videotapes of street

block attributes, conducted onsite observations and interviews, and reviewed

police officer patrol logs to develop a

comprehensive view of factors contributing to the random gunfire problem.

Oakcliff is composed primarily of residential rental units mixed with light

industrial and commercial enterprises.

The community is situated between two

major commercial corridors with a park

and large lake on its northern border.

The majority of Oakcliff residents are

economically poor and lease their apartments. Fewer than 20 percent of the

Oakcliff residents own their own homes,

compared with a citywide ownership rate

of more than 50 percent and a nationwide

ownership rate of 59 percent.12 The average monthly rent in the Oakcliff community is $295. By contrast, more than

90 percent of Dallas residents pay more

than $300 in rent per month, and, of

these renters, 41 percent pay $500 or

more per month.13

Oakcliff reports high levels of random

gunfire: 422 citizen reports of random

gunfire shots per 10,000 people per year

in the 1-square-mile neighborhood alone.

Although random gunfire calls represented 1.1 percent of total police service calls

citywide, they represented 4.6 percent of

that focus specifically on random gunfire

problems. In cities such as Dallas (the

police department’s Gunshot Awareness

Program), New Orleans (Gunshot Public

Awareness Program), Redwood City

(Operation Silent Night Program), and St.

Louis (Town Criers’ Program), community

awareness campaign volunteers and the

police work together to inform people of

the dangers of random gunfire.

Anecdotal evidence from newspaper

articles,6

 television broadcasts,7 and

interviews with police department officials8

 and community members9 suggests

that random gunfire is a serious problem

in many cities. Residents in these communities live in perpetual fear: they worry

that a stray bullet will kill an innocent bystander; they feel they live in the middle

of a war zone on some nights; they hide in

their homes, afraid to confront the people

disrupting their lives; and law-abiding

business owners and residents are willing

to abandon or relocate from a neighborhood with random gunfire problems.10

One Redwood City resident summed up

the problem by stating:

It is not uncommon to find bullets

lodged in front porches or gutters.

We are afraid for our children.

The random gunfire problem is also

costly in terms of law enforcement,

property damage, and declining

property values.

The number of deaths from firearmsrelated injuries is recognized as a significant national public health problem. In

the United States in 1996, for example,

there were 12.8 deaths per 100,000

people caused by firearms-related injuries. For males 15 to 24 years old, the

problem is even more staggering: in 1996,

there were 38.9 deaths from injuries sustained by firearms per 100,000 people.11

These data are a composite of firearmsrelated deaths and do not differentiate between intentional and accidental firearms

gunfire is strictly an outdoor

activity; (2) it is not usually part of

other criminal activity such as drug

dealing, assaults, or robberies; and

(3) random gunfire shooters do not

fire their weapons to intentionally

injure or kill people.

Residents in communities with high

levels of random gunfire live in perpetual fear; and law-abiding business owners and residents freely

express their willingness to abandon or relocate from a neighborhood with random gunfire

problems.

Key findings: The study of the use

of gunshot detection technology

in local law enforcement led the

research team to four broad

conclusions:

● Gunshot detection systems are

likely to reveal rather high citizen

under-reporting rates of random

gunfire problems (23 percent of

incidents are reported).

● The technology is likely to increase the workloads of police

officers, particularly if departments

dispatch a patrol unit to every

gunfire incident detected by a

technological system.

● Gunshot detection systems are

not likely to lead to more arrests

of people firing weapons in urban

settings because it is highly unlikely

that offenders will stay at a gunshot location long enough for the

police to arrive.

● Finally, gunshot detection

systems seem to offer the most

potential as a problem-solving tool

and would fit nicely within the

emerging problem-oriented policing paradigm. The technology can

help police identify random gunfire

hot spots and develop strategies to

address the problem.

Target audience: Local police

administrators, local government

officials, community groups, and

researchers.

Issues and Findings

continued...
3

R e s e a r c h i n B r i e f

mitter. Eighty-six pole units were

erected in the 1-square-mile Oakcliff

target area to provide adequate system

coverage for the 2-month study

period.18

The pole units are designed to acoustically identify gunshots and transmit

that information to a police dispatch

center through a network of transmitters and receivers connected to the

local phone system. The gunshot location and time are transmitted to a personal computer in the dispatch center

in less than 2 seconds, and the gunfire

information is displayed on a computerized map, enabling dispatchers to

relay the information to officers on

the street.

The SECURES prototype alerts police

dispatchers to the location of the first

pole unit to detect a shot. ATI claims,

however, that subsequent enhancements to the system “triangulate”

gunfire alerts such that real-time

information from responding pole units

pinpoint the precise location from

which the shot was fired. ATI claims

this type of “triangulation” procedure

can pinpoint 99 percent of gunshots

within a 65-foot radius of the firing

spot, 88 percent of gunshots within

30 feet, 63 percent of gunshots within

20 feet, and 35 percent of gunshots

within 10 feet.19

Trilon Technology’s ShotSpotter.

The ShotSpotter gunshot detection

technology installed in Redwood City

was designed and demonstrated by

Trilon Technology. The ShotSpotter

system, installed in the 1-square-mile

Redwood Village area since early

1996, consists of eight acoustic sensors, a central computer located in the

Redwood City Police Department’s

dispatch center, and gunshot detection

and location identification software.

total calls for service in Oakcliff during 1996. Police report no random

gunfire calls for 65 percent of Oakcliff

streets (similar to call patterns for

other crime problems). However, a

small percentage (5.5 percent) of the

streets generated nearly 45 percent of

all random gunfire calls.14

Researchers examined the social and

physical attributes of Oakcliff street

blocks that experienced random gunfire calls for service. These results are

specific to the Oakcliff neighborhood

and cannot be generalized to Dallas or

any other community in the United

States. The research shows predominately residential street blocks that

had higher property values or rental

fees experienced more random gunfire

calls for service than Oakcliff street

blocks with lower property values or

those comprising commercial properties or vacant blocks.15 Random gunfire calls were not generally a problem

on Oakcliff street blocks that had a

large proportion of properties in disrepair or on streets with high levels of

physical decay, a lot of foliage, or on

blocks with relatively high levels of

calls about serious crime problems.16

Random gunfire calls were more

prevalent on street blocks that generated a substantial number of prowler,

suspicious person, and disturbance

calls. This suggests other types of suspicious and unruly behavior are probably correlated with Oakcliff’s random

gunfire problem.

The study findings are somewhat

inconsistent with crime and place

research that finds signs of decay are

indicative of other social and crime

problems.17 Nevertheless, the study

findings suggest random gunfire may

be a unique type of crime problem not

necessarily part of, nor indicative of,

systemic decline and decay on a street

block. The study results are consistent

with Dallas police officer perceptions

that random gunfire problems occur

in Oakcliff’s residential areas, specifically in the context of people drinking

in their homes and backyards, watching sporting events, and celebrating.

Gunshot detection systems

What are they? Acoustic gunshot

detection systems are designed to pick

up the sound of a muzzle blast from a

gun and, within seconds of the shot being fired, pinpoint or triangulate within

some margin of error the gunshot’s

location, before alerting the police

about the shot being fired.

Manufacturers of gunshot detection

systems expect the technology to increase the ability of the police to get to

the scene of random gunfire quickly,

increase the number of people arrested

for firing weapons, and reduce the detrimental effects (injuries, fear, disinvestment) of shots being fired in urban

settings. Community advocates of

gunshot detection systems believe the

technology can deter would-be shooters and improve the quality of life in

their neighborhoods.

Alliant Techsystems Inc.’s

SECURES. The gunshot detection

system installed in Oakcliff was

developed and demonstrated by

Alliant Techsystems Inc. (ATI) and

subsequently marketed as SECURES

(System for the Effective Control of

Urban Environment Security).

SECURES identifies the location and

time of gunfire in a specified target

area through a series of small units (or

acoustic sensor modules) mounted on

utility poles. These battery powered

“pole units,” which are about the size

of a video cassette, are composed of an

acoustic sensing element, gunshot

identification electronics, and a trans-
4

R e s e a r c h i n B r i e f

The acoustic sensors include microphones, acoustic sensing elements,

and gunshot identification electronics.

The sensors installed in Redwood Village resemble birdhouses and heating

vents and are enclosed in weatherproof

containers approximately 1 cubic foot

in size. The acoustic sensors detect

muzzle blasts from gunfire or other

explosions and then transmit the

sound of the gunfire via telephone

line to a central computer located in

a police department dispatch center.

Parameter settings in the ShotSpotter

software determine the system’s level

of sensitivity: if the thresholds are set

quite high, background noise is less

often identified as gunfire. Conversely,

if the thresholds are set quite low,

more background noise can be detected as gunfire, increasing the potential that extraneous noises will be

incorrectly identified as gunfire.20

Once the sensors detect a sound and

transmit the information to the central

computer, the ShotSpotter software

discriminates against most other community sounds (such as car backfires,

jackhammers, thunder, and barking

dogs) and pinpoints the location of the

gunfire or explosions. Gunshot events

are displayed on a computer map in

the police dispatch center within approximately 15 seconds of the noise

being made. The computer map distinguishes property boundaries, including

front or side yards, curbsides, or street

corners.

Determination of the precise location

of gunfire events is conducted through

a series of iterations of triangulation

algorithms. The system can generate

an overview map that presents the

locations of historical shootings to

discern patterns in space or time. The

ShotSpotter computer can be placed in

a dispatch center with stand-alone or

integrated outputs, or it can be placed

at a remote site.21

The ShotSpotter system stores all

waveforms for every detected gunfire

event and 6 seconds of audio from

each detecting acoustic sensor

(2.3 megabytes each). As such, a

significant amount of system memory

is required when numerous gunfire

events occur simultaneously or when

many noises are relayed to the system

in quick succession (during New

Year’s Eve or Fourth of July, for example). Once the ShotSpotter system

detects a shot and reports the location

on the computer screen, dispatchers

can play back the 6-second snippet of

sound from any sensor to assist them

in determining what they believe to be

the true source of the sound: firecracker string, multiple gunshots,

shotgun blast, or car backfire. The

ability to play back the sound of the

apparent gunfire alert is unique to

ShotSpotter and offers police an opportunity to determine whether they think

the sound is in fact gunfire.

Do they work?

The Redwood City Police Department,

the San Mateo County Sheriff’s Office,

and Trilon Technology agreed to submit the ShotSpotter system to a series

of field trials. The police department

approved the firing of test blanks under controlled conditions to measure

the performance of the technology in

June 1997.22 Similar permissions were

not granted during the field test of the

SECURES system in Dallas.

The evaluation team worked with police department personnel to select

weapon types, the number of shots to

be fired, and the times and locations

from which test shots would be fired.

The police suggested that three

weapon types be used: an MP5 assault

rifle, a .38 caliber pistol, and a 12

gauge shotgun. The police department

notified community residents and

business owners about the inordinate

number of shots that would be fired

during the field test to avoid calls from

concerned citizens about the gunfire.

All test shots were fired from sidewalks at intersections or along street

blocks.

The evaluation team assessed the

performance of the ShotSpotter system

based on three outcomes:

● Did the ShotSpotter gunshot

detection system annunciate and

triangulate the “shot” location

(true positive)?

● Did ShotSpotter fail to annunciate

or triangulate the “shot” location

(false negative)?

● What was the location error from

the true shot location to the triangulated shot location (in feet)?

Exhibit 1 presents the results of the

field trial, examining the breakdown of

results for each weapon type and each

of the evaluation outcomes (annunciation and location error).

Of the 31 field trial events, 8 tested

the MP5 assault rifle, 13 tested

the .38 caliber pistol rounds, and

10 tested the 12 gauge shotgun. The

technology annunciated shotgun tests

at the highest rate (90 percent), followed by pistol tests (77 percent), and

the MP5 assault rifle (63 percent).

Overall, the ShotSpotter technology

annunciated nearly 80 percent of the

test shots (true positives) and failed

to annunciate random gunfire events

about 20 percent of the time (false

negatives). It should be noted that the

muzzle blast waveform from blank

rounds is different from the muzzle
5

R e s e a r c h i n B r i e f

blast waveform from live rounds; it can

be difficult for gunshot detection technologies to discriminate between the

two.23 Therefore, the ShotSpotter technology should annunciate significantly

more than 80 percent of gunfire incidents when live rounds are fired under

real-life conditions.

The ShotSpotter system identified and

triangulated random gunfire events

within about 25 feet of the true shot

location. Shotgun events had the lowest median location error of 23.5 feet;

pistol events were correctly identified

within 25 feet of the true shot location;

and the MP5 assault rifle tests were

identified within 27 feet of the correct

firing location.

Random gunfire alerts and

police response

Citizen reporting of a gunshot fired is

typically dependent on (1) the citizen

hearing the shot, (2) the citizen identifying the noise to be gunfire, (3) the

citizen making the decision to call the

police shortly after the shot has been

fired, and (4) the citizen telling the

police the location from which the

shot was fired. Prior to the introduction of the gunshot detection system in

Dallas, the police took approximately

20 minutes to dispatch a citizen call

about random gunfire and an additional 5 minutes to respond (arrive on

the scene) to citizen alerts in the study

area. This response pattern was consistent with the low priority response

the police department placed on random gunfire calls. Officers typically

stayed on the scene of a call for about

15 minutes. In total, citizens’ random

gunfire reporting calls took approximately 40 minutes to clear from the

time the call was placed to the time

the officer concluded the investigation

of the scene.24

The introduction of gunshot detection

systems in Dallas removed the citizen

contingencies influencing random

gunfire reporting and somewhat

changed the patterns of police response. During the field trial in Dallas,

the police received 188 alerts of gunfire from the SECURES system and

49 citizen calls. They subsequently

dispatched 151 of the SECURES

alerts and 39 of the citizen calls.25

The police dispatched both citizen

calls and SECURES alerts quicker

during the field trial (13 minutes and

18 minutes, respectively) than before

the introduction of the gunshot location system. The police continued to

take about 5 minutes to arrive on

the scene for a citizen alert and about

7 minutes for a SECURES alert. Once

on the scene, the police cleared the

citizen call quicker (12 minutes) than

before the field trial, yet they took

significantly longer to clear the

SECURES alert (19 minutes). It is

possible the police spent less time on

citizen calls about random gunfire due

to the greater total number of random

gunfire alerts generated by the gunshot

location system and the subsequent

increase in the number of dispatches

for random gunfire alerts.26 Overall,

the Dallas police received and cleared

citizen random gunfire calls in about

30 minutes, and they received and

cleared SECURES alerts in about

44 minutes during the field trial.

Using gunshot detection

systems

During the 2-month Dallas field trial,

the police made 190 radio runs (151

SECURES alerts and 39 citizen random

gunfire calls) in the 1-square-mile

Oakcliff community.27 The number of

citizen calls during the field trial was

similar to the average number of citizen calls to the police about random

gunfire incidents prior to the field

trial.28 As such, the extra SECURESdispatched radio runs over and above

the citizen-initiated calls during the

field trial represent an almost fivefold

increase (190/39=4.87) in the number

of police dispatches to random gunfire

problems.

Alliant Techsystems Inc. claims

SECURES correctly identifies 88

percent of all shots whose propagation

path to the microphone is not blocked

by a close building.29 The acoustic

database used to support this claim

was collected by ATI during tests

conducted at military proving grounds

and police test ranges and when live

rounds were fired in open field environments as well as among building

structures.30 Thus, assuming the SECURES true-positive rate is correct,

the field trial suggests that many random gunfire incidents are not reported

by citizens.31

Exhibit 1. Redwood City’s ShotSpotter Field Trial Results

Total Number Percent of Median

of Gunfire Shots Location

Events Annunciated Error (In Feet)

MP5 Assault Rifle 8 63 27.0

.38 Caliber Pistol 13 77 25.0

12 Gauge Shotgun 10 90 23.5
6

R e s e a r c h i n B r i e f

How should the police respond to an

inordinate increase in random gunfire

alerts? Indeed, introduction of the

technology challenges the police to

carefully consider the manner in

which they mobilize their resources to

respond to alerts: on the one hand, the

technology provides police with much

more information about random gunfire problems than previously generated through citizen calls. If the ATI

claim that SECURES fails to detect

only 12 percent of all shots and if the

citizen reporting figure of 23 percent

of all random gunfire incidents in the

Dallas field trial is accurate,32 then

one can reasonably conclude that gunshot detection systems provide the

police with important insights as to

the nature, extent, and locations of

random gunshots.

On the other hand, the increase in random gunfire alerts has the potential to

significantly influence the delivery of

police services. The nearly fivefold increase in radio dispatches represents a

significant increase in the police

workload for a very small geographic

area (less than 1 square mile). Moreover, during the study period, not a

single arrest was made in response to a

dispatch for random gunfire in Dallas,

and police officers patrolling Oakcliff

spent less time processing citizen calls

for random gunfire during the field test

(compared with the time spent on

citizen calls before the field trial) to

handle the large increase in radio runs

generated by the SECURES technology.33

What do police think of

gunshot detection systems?

Patrol officers from both the Dallas

and Redwood City police departments

were surveyed about their perceptions

of the impact of gunshot detection

systems on their work routine, their

confidence in the technology to report

gunfire incidents, and their perceptions of the ability of the technology

to improve police effectiveness in

handling such incidents. All officers

assigned to areas in which the technology was deployed and they could

possibly be dispatched to gunshot incidents received questionnaires. In

Dallas, 58 percent (124 of 212) of

patrol officers completed the questionnaires, while in Redwood City, 66

percent (27 of 41) of patrol officers

returned the questionnaires.

As happens with many technological

and strategic innovations introduced

into police departments,34 patrol officers from both Dallas and Redwood

City reported some frustrations with

the gunshot detection systems. They

generally lacked confidence in the

ability of the systems to identify and

locate gunfire occurrences. They also

worried about false alerts, and they

expressed concern about the time

spent responding to gunfire alerts and

the low likelihood of catching or arresting the shooter.

Officers in both cities feel they are

more likely to talk with citizens when

responding to citizen-generated calls

than to gunshot detection system calls,

and they make more problem-solving

progress on citizen alerts than technology alerts. Generally, officers feel

citizen calls about gunfire give them

a focal point in responding to the call.

Officers can ask the citizen about what

he or she heard, and they can glean

details about the context of the shot

fired. By contrast, officers explain that

the gunshot detection systems provide

no details about the apparent shot,

leaving them without any guidance to

pursue an investigation.

Summing up

The study of the use of gunshot detection technology in local law enforcement led the research team to four

broad conclusions:

● Gunshot detection systems are

likely to reveal rather high citizen

under-reporting rates of random

gunfire problems.

● The technology is likely to increase

the workloads of police officers,

particularly if departments dispatch

a patrol unit to every gunfire incident detected by a technological

system.

● Gunshot detection systems are not

likely to lead to more arrests of

people firing weapons in urban settings because it is highly unlikely

that offenders will stay at a gunshot

location long enough for the police

to arrive.35

● Finally, gunshot detection systems

seem to offer the most potential as

a problem-solving tool and would

fit nicely within the emerging

problem-oriented policing paradigm. The technology can help

police identify random gunfire hot

spots and develop strategies to

address the problem.

Notes

1. Egan, Timothy, “Police Surveillance of

Streets Turns to Video Cameras and Listening

Devices,” The New York Times, Feb. 7, 1996;

and Kass, Jeff, “Police Aim to Silence

Celebratory Guns at New Year’s,” The Los

Angeles Times, Dec. 17, 1995: B1 and B13.

2. Dallas Police Department, Random Gunfire

Reduction Proposal, Dallas, TX: Dallas Police

Department, 1993.

3. Page, Edward, and Brian Sharkey,

“SECURES: System for Reporting Gunshots in

Urban Environments,” Society of Photo-Optical

Instrumentation Engineers. 2497 (1995): 160.
7

R e s e a r c h i n B r i e f

4. Interview with Dallas Police Department

personnel, Dec. 14, 1996.

5. Kennedy, David, Anne Piehl, and Anthony

Braga, “Youth Violence in Boston: Gun Markets, Serious Youth Offenders, and a Use

Reduction Strategy,” Law and Contemporary

Problems. 59 (1) 1996: 147–159; also see

Sherman, Lawrence W., and Dennis P. Rogan,

“Effects of Gun Seizures on Gun Violence: ‘Hot

Spots’ Patrol in Kansas City,” Justice Quarterly

12 (4) 1995: 673–693.

6. Associated Press, “Ringing in ’97 With

Bullets, Bombs; Police, Fire Officials Prepare

for Illegal New Year’s Revelry,” The Lubbock

Avalanche, Dec. 31, 1996; see also Pimental,

Benjamin, “Redwood City OKs Test of System

to Locate Gunshots: First City to Use the New

Sensors,” The San Francisco Chronicle, Aug.

30, 1995: A16; “Support Builds for Gunshot

Locator,” The San Jose Mercury News, Feb. 12,

1997: 1B and 4B.

7. CBS Evening News, “New High Tech Help

for Tracking Down Criminals,” CBS Evening

News, Jan. 17, 1996; ABC Evening News,

“Redwood City Council Votes to Purchase

ShotSpotter after Successful Test,” ABC

Evening News, July 28, 1997; Channel 10

San Diego, “Does ShotSpotter Really Work?”

Channel 10 San Diego, Aug. 27, 1998.

8. Based on personal communications, interviews, and discussions with Dallas Police

Department and Redwood City Police Department representatives in 1996 and 1997.

9. Focus groups conducted with Redwood City

residents in June 1997.

10. Personal communication with Redwood

City residents in 1997.

11. National Vital Statistics Report. 47 (19)

June 30, 1999.

12. U.S. Census Bureau, Census of Population

and Housing: General Profile for the United

States, Washington, DC: U.S. Department of

Commerce, U.S. Census Bureau, 1990.

13. U.S. Census Bureau, Census of Population

and Housing: General Profile for Dallas City,

TX, Washington, DC: U.S. Department of

Commerce, U.S. Census Bureau, 1990.

14. Sherman, Lawrence, Patrick Gartin, and

Michael Buerger, “Hot Spots of Predatory

Crime,” Criminology 27 (1) 1989: 27–56; also

see Watkins, C., “Environmental Correlates of

Random Gunfire: A Block Level Analysis of

the Relationship between Random Gunfire

Problems and Physical and Social Incivilities,”

unpublished doctoral dissertation, University of

Cincinnati, 1998.

15. Oakcliff is a designated “dry” neighborhood. As such, no public bars or liquor stores

operate in the neighborhood. However, private

drinking clubs exist in Oakcliff, primarily in

residential areas.

16. Watkins, C., “Environmental Correlates of

Random Gunfire: A Block Level Analysis of

the Relationship between Random Gunfire

Problems and Physical and Social Incivilities.”

17. Eck, John, and David Weisburd, “Crime

Places in Crime Theory,” in Crime and Place,

ed. J.E. Eck and D. Weisburd, Monsey, NY:

Criminal Justice Press, 1995; Mazerolle,

Lorraine Green, Jan Roehl, and Colleen

Kadleck, “Controlling Social Disorder Using

Civil Remedies: Results from a Randomized

Field Experiment in Oakland, California,” Civil

Remedies and Crime Prevention: Crime Prevention Studies, vol. 9, Monsey, NY: Criminal Justice Press, 1998: 141–160; Skogan, Wesley,

Disorder and Decline: Crime and the Spiral to

Decay in American Cities, New York: Free

Press, 1989; Taylor, Ralph, “Social Order and

Disorder of Street Blocks and Neighborhoods:

Ecology, Micro Ecology and the Systemic

Model of Social Disorganization,” Journal of

Research in Crime and Delinquency 34 (1997):

113–155; Wilson, J.Q., and G. Kelling, “Broken Windows,” The Atlantic Monthly, March

1982: 29–38.

18. ATI personnel in an Oct. 30, 1996, interview said the pole units cost about $1,750

each, and the batteries last about 2 months.

They suggest that approximately 80 pole units

are required to cover a 1-square-mile area.

To lease, SECURES will cost approximately

$5,500 for each square mile covered per

month. This cost covers the lease of 100 pole

units, 3 repeaters, 1 base station, and maintenance on the system. The quoted cost does not

cover installation and assumes medium density

housing.

19. Alliant Techsystems Inc. failed to install the triangulation enhancement of the

SECURES system at the time of the field trial.

Officers were dispatched to the first pole unit

that recorded a shots-fired incident rather than

a triangulated location identified through a

series of detections by numerous pole units.

(Based on an Oct. 30, 1996, interview with

ATI personnel.)

20. Muzzle blasts from gunfire have distinctive

waveforms, as do the sounds from other similar

sources. However, the setting parameters determine what level of extraneous noise will trip

the system. Hence, the less sensitive the parameter settings, the less likely it is that jackhammers, thunder, and car backfires will set

the system off (false positives). Alternatively,

the more sensitive the parameter settings, the

more likely it is that extraneous noise will trip

the system.

21. The system can be its own operating system

within the dispatch center, or it can be linked

into the dispatch system’s operating system.

22. The original proposal was to discharge live

rounds of ammunition. However, numerous

discussions with the police chief, his advisers,

and personnel from Trilon Technology led to

an agreement to discharge blanks as opposed to

live rounds. Although the amplitude waves

generated by blanks are not identical to the

amplitude waves generated by live ammunition,

they were close enough for the blanks to serve

as adequate substitutes.

23. Personal communication with John Collins,

ed., Association of Firearm and Toolmark Examiners Journal, Nov. 9, 1999.

24. Comparative response time data were not

readily available in Redwood City. Calls were

placed to both the San Mateo County Sheriff’s

Office and the Redwood City Police Department. Only selected calls were available for

analysis from the police department data,

compromising a complete analysis of their

call data.

25. Mazerolle, Lorraine Green, Cory Watkins,

Dennis Rogan, and James Frank, “Using Gunshot Detection Systems in Police Departments:

The Impact on Police Response Times and

Officer Workloads,” Police Quarterly 1 (2)

1998: 21–49.

26. Ibid.

27. There were 151 SECURES alert “events”

that were not linked at any time to a citizen

call and resulted in a radio run. There were

39 citizen alert events during the study period

resulting in 39 radio runs. Of these 39 citizeninitiated radio runs, 10 included a SECURES

alert that was “referenced” to a citizen call.

That is, the call-taker and/or dispatcher linked

the SECURES call to the citizen call and dispatched it as a citizen call. As such, a total

of 190 radio runs for random gunfire alerts

were made during the study period: 151 that
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involved the technology only, 29 that involved

citizen calls only, and 10 that were dispatched

as citizen calls but involved a combination of

citizens and SECURES initiating the alert.

28. See Mazerolle et al., “Using Gunshot

Detection Systems in Police Departments:

The Impact on Police Response Times and

Officer Workloads.”

29. Page and Sharkey, “SECURES: System for

Reporting Gunshots in Urban Environments”:

170.

30. Ibid.: 162.

31. The research team cannot provide any

independent measure of this claimed falsepositive rate because no field test of SECURES

was conducted in Dallas where blank or live

rounds were fired under field trial conditions.

32. The 23-percent citizen reporting rate was

reached in the following manner: using the

baseline of 151 SECURES-initiated radio runs

during the 2-month field trial, researchers applied the 12-percent error rate to identify 169

estimated shots. The 39 citizen-initiated radio

runs over the test period were divided by the

169 estimated incidents to identify the 

23-percent reporting rate (39/169x100).

33. Officers in both cities believe they tend to

respond quicker to gunshot detection system

calls than citizen-generated calls. Some officers explained they merely want to clear the call

quickly and move on to the next call. It is reasonable to expect that the police would spend

more time handling calls that they thought

worthwhile. Possible explanations for these

apparent contradictory findings: (1) the police

“leave open” the SECURES alerts longer because there is no citizen waiting to talk with

them when they arrive, and they move on to the

next call; (2) police deal with a citizen-initiated

alert in a more expedient manner because

there is a set of standard procedures to follow

Findings and conclusions of the research

reported here are those of the authors and do

not necessarily reflect the official position or

policies of the U.S. Department of Justice.

Lorraine Green Mazerolle, Ph.D., is an

associate professor in the Division of

Criminal Justice at the University of

Cincinnati. Cory Watkins, Ph.D., is

assistant professor in the Department of

Criminal Justice and Legal Studies at

the University of Central Florida. Dennis Rogan, Ph.D., is president of Statistical Analysis for Law Enforcement

Strategies in Bowie, Maryland. James

Frank, Ph.D., is associate professor in

the Division of Criminal Justice at the

University of Cincinnati. The study

reported in this Research in Brief was

supported by grant # 96–MU–MU–0018

from the National Institute of Justice to

the University of Cincinnati.

The authors are indebted to support from

the Dallas Police Department, the Redwood City Police Department, Alliant

Techsystems Inc., and Trilon Technology.

Please address all correspondence to

Lorraine Green Mazerolle, Associate

Professor, Division of Criminal Justice,

University of Cincinnati, PO Box 210389,

Cincinnati, OH 45221–0389. Phone

513–556–5830, fax 513–556–3303, or

e-mail Lorraine.Mazerolle@uc.edu.

NCJ 179274

The National Institute of Justice is a

component of the Office of Justice

Programs, which also includes the Bureau

of Justice Assistance, the Bureau of Justice

Statistics, the Office of Juvenile Justice and

Delinquency Prevention, and the Office for

Victims of Crime.

This and other NIJ publications can be

found at and downloaded from the NIJ

Web site (http://www.ojp.usdoj.gov/nij).

(i.e., visit the caller, elicit information from

them, and then take a look around). This is not

the case for the SECURES alerts. The police

get to the scene and then have to knock on a

few doors to gather information about the

gunfire.

34. Chatterton, Michael, “Targeting Community Beat Officers: Organisational Constraints

and Resistance,” Policing and Society 3

(1993): 189–203.

35. One caveat here is the initiative recently

announced by Trilon Technology called

“The Communicator,” which is linked with the

ShotSpotter system to systematically place calls

to households and businesses within a close

geographic area of the gunfire alert to inform

them of the incident. If the citizen has information, he or she can press a key on a touch-tone

phone to be immediately transferred to a live

dispatcher.