Through-the-Wall Surveillance: A New Technology for Saving Lives
by Christopher A. Miles
About the Author
Mr. Miles is the biometrics program manager within the Human
Factors Division of the U.S. Department of Homeland Securitys
Science and Technology Directorate. He is the former senior
program manager of NIJs sensor and surveillance portfolio.
All products and manufacturers cited in this document are
presented for informational purposes only and do not constitute
product approval or endorsement by the National Institute
of Justice.
Actor Kevin Costner said it best in the 2006 movie The
Guardian, in which he played a legendary U.S. Coast Guard
rescue swimmer. During a conversation with one of his young
charges, he said, There will come a time when you might
have to decide who lives and who dies out there. Its a
terrible responsibility, but its one you will have to
make . . . . The bigger reality is its also something you
are going to have to live with as a human being.
With life and death on the line, it is impossible to overstate
the value of new technologies that save lives, especially
when they reduce the risk to citizens, law enforcement
officers, and soldiers. One such technology is through-the-wall
surveillance (TWS).
TWS technology helps officers to determine if someone is in
a room before putting themselves in harms way and to save
lives by using motion and images to differentiate between
a hostage and a hostage-taker. It can also detect motion
through floors and rubble following a building structure
failure and, therefore, help in the search for survivors.
It allows users to conduct room-to-room searches for
suspected terrorists, map the interior of buildings, and
find military combatants and weapons cachesall through
an interior or exterior building wall. Certain TWS
technologies do not even need to be placed against a wall
and can be used to perform standoff searches, for example,
from a vehicle into a building.
Value to Law Enforcement
In the field of law enforcement, the possibility of officer
injury and death is all too real. In the decade between 1996
and 2005, more than a half million (566,626) officers were
assaulted in the line of duty. In that same period, 575
officers were killed19 of them during tactical situations
involving barricaded offenders, hostage-taking, and high-risk
entry.[1]
These situations involve the riskiest of conditions for law
enforcement, and consequently, many agencies have specially
trained emergency response teams (ERTs) or special weapons
and tactics (SWAT) teams to handle them. ERTs and SWAT
teams often have access to specialized firearms and weapons,
heavy body armor and ballistic shields, equipment for forced
entry, covert communications, video and audio surveillance
technologies, and special vehicles that can help improve
responses and increase safety.
TWS technology could undoubtedly help these men and women
in the field (see sidebar, Through-the-Wall
Surveillance: Reducing Risk to Law Enforcement). With
the potential benefits of this technology, however, come
concerns about high cost, limitations in ability, and
privacy and policy issues. These areas must be addressed
to ensure that this technology is developed and implemented
effectively to reduce the risk to law enforcement and
save lives.
Iraq: The Wars Role in TWS Evolution
TWS technology typically has been developed for military use;
however, it is now transitioning to law enforcement as costs
have become more affordable. Although TWS has been the subject
of research and development for the past 10 years, the war
in Iraq has moved it to the forefront. The Defense Advanced
Research Projects Agency (DARPA), the central research and
development organization for the U.S. Department of Defense,
rapidly introduced the Radar Scope device, a portable handheld
device designed to penetrate 12 inches of concrete and 50
feet beyond that into a room.[2]
Barely larger than todays stud detectors, weighing only 1.5
pounds, and running on two AA batteries, the Radar Scope
reliably detects motion as slight as breathing and transmits
information on where in the room the motion is occurring.
With a projected price of $1,000, this technology is expected
to make a quick transition to SWAT teams and, most likely,
to general law enforcement.
DARPA has also provided support for a larger SoldierVision
device, which creates a two-dimensional color image depicting
range and distance to objects in motion.
This device penetrates 60 feet into a room and has a standoff
capability, allowing it to be 30 feet away from a wall and
still penetrate 30 feet into the room. It can provide
intensive target detection out to 9 feet, detecting someone
hiding in a closet or a crawl space, for instance. Although
the SoldierVision device does not comply with Federal
Communications Commission (FCC) certification for use in the
United States,[4]
another version, the RadarVision2 device,
is FCC certified.[6]
The range of the RadarVision2, however, is cut in half,
providing a penetration of 30 feet into rooms. It also sells
for more than $20,000, putting it out of reach for many law
enforcement agencies.[7]
On the high-end of TWS capabilitiesand priceis
the Camero Xaver™ 800 product, which produces a 3-D
display of a room in real time.[8]
Full 3-D imaging can be accomplished up to 26 feet, and it
has an extended imaging range of up to 65 feet. Operators
can see not only the shape of the room, but also figures
moving around or in one place within the room. A persons
height and distance from walls or objects can be estimated
quite easily. The system is generally considered too expensive
for law enforcement. Its manufacturer is currently developing
a Xaver™ T system, which should be lower in cost.
Current Limitations of TWS Technology
Current TWS technology is limited in what it can do. Metal
in walls and metal-backed insulation can block the ability to
see into a room, and most TWS technologies provide a lower
resolution image compared to video images. Each pixel in the
TWS image represents an inch or more across the target,
making it very difficult to differentiate between a cell
phone and a handgun, for instance.
Although the ability to produce images of moving people,
fixed objects, and room structure makes this technology very
attractive to law enforcement, systems that offer an actual
video currently are too expensive for police departments.
Meanwhile, the less expensive systems provide only an
indicator of motion on the other side of a wallwhich,
for example, could be an armed person or an animal.
Privacy Issues Exist
TWS technology raises significant privacy issues: Does it
violate a persons Fourth Amendment right against unreasonable
search and seizure?
In some situations, this technology would constitute an
unreasonable search of a home unless a warrant with probable
cause had been issued. The primary exception would be in
emergency or exigent conditions. There is a significant
body of case law that describes such conditions; perhaps
the clearest explanation is:
A search is reasonable, and a search warrant is not
required, if all of the circumstances known to the officer
at the time would cause a reasonable person to believe that
entry or search was necessary to prevent physical harm to
the officer or other persons, the destruction or concealment
of evidence, the escape of a suspect, and if there was
insufficient time to get a search
warrant.[9]
In tactical situations involving barricaded offenders and
hostage-takingsituations in which there is not sufficient
time to obtain a search warrantit is fairly reasonable
to assume that the use of TWS technology would prevent
physical harm to an officer or other person. When serving
high-risk warrants, however, it is not reasonable to assume
that there is insufficient time to get a search warrant for
a known address. In other words, even though serving a
high-risk warrant may present a risk to law enforcement, the
serving of the warrant is not typically time-critical. Thus,
using TWS technologies to search a premises would require
the appropriate search warrant under current legal precedent.
The use of TWS technologies in all situations must follow
clearly defined policies and procedures that have been vetted
by an agencys command and legal staff.
Federal Coordination
In the 1990s, the Technology Policy Council (TPC) was formed
at the direction of the U.S. Attorney General to provide a
forum for Federal agencies to share information about their
research and development of law enforcement technology.
Administered by the National Institute of Justice (NIJ),
TPC provides an opportunity for agencies throughout the
Federal Government to leverage projects, where it makes
sense, to avoid duplication of efforts and to maximize the
return on investment. The Deputy Attorney General serves
as the chair of TPC.
At a December 2006 TPC meeting sponsored by the U.S. Department
of Justice, representatives from several government agencies
shared information on their TWS technology programs. The
meeting revealed significant interest and investment in
detecting objects and people in buildings and providing
surveillance into a structure prior to entry. The meeting
also revealed the need for standards and test protocols
to ensure that:
- Performance is objectively measured and evaluated in
the laboratory and in the field.
- Systems are interoperable with datasharing and command
and control environments.
- Performance objectives for future research and development
are realistically set.
Federal agencies will continue to coordinate to ensure that
they have identified and discussed the important issues
surrounding privacy and human subject impact assessments.
Without an upfront understanding of the legal and health
implications posed by TWS technology, criminal justice
agencies could face problems they had not consideredproblems
that may be easily avoided through coordination and policy
planning.
Where to Go From Here?
TWS technology continues to evolve and improve. In July 2006,
the Office of Naval Research initiated a Transparent Urban
Structures program to collect and integrate information to
determine the intent of above- and below-ground structures
and quickly get the right data to the right
user.[10] The
program seeks to provide military personnel with an intuitive,
portable interface that presents a clear, real-time picture
of the battlefield and threats, likely enemy courses of
action, and actionable intelligence of the situation
surrounding them.
DARPA has a major program under way called Visibuilding,
which is developing further technologies for sensing people
and objects in buildings.[11]
A key component of this project is making technology useful
during a range of operationsfrom pre-mission planning
to find which buildings should be searched, through post-mission
analysis to find hidden objects or people.
NIJ is also working to advance TWS research, development,
and evaluation through its sensors and surveillance portfolio
and solicitation for proposals.[12]
Through a 2006 solicitation, the Institute is funding a
research project to add an acoustic TWS capability to the
TimeDomain system, which uses ultrawide band radar TWS
technology. Because radar currently is blocked by metal
walls or aluminum-backed insulation, an acoustic capability
would allow the TWS device to provide some surveillance
capability to penetrate through those walls. A prototype
system integrating radar and acoustic capabilities should
be complete in early 2008.
As the capabilities, cost, and availability of TWS technology
continue to improve, there will be many more opportunities
to save lives by reducing the risk to law enforcement in
tactical situations so that officers can make quicker,
smarter, life-saving decisions.
NCJ 219607
Sidebars
EVALUATING THROUGH-THE-WALL SURVEILLANCE TECHNOLOGY
The
National Institute of Justice (NIJ) is currently evaluating
through-the-wall surveillance (TWS) technologies in a
controlled environment. The Institute has funded the
construction of test walls at the Air Force Research
Laboratory in Rome, New York, where the efficacy of some
TWS technologies is being tested. Such controlled evaluations
set clear performance criteria, allow comparisons between
systems that are commercially available, and define future
research and development priorities.
NIJ also loans technologies to law enforcement and corrections
officers for evaluation in real-world situations. These
officers often find creative ways to use the technology not
envisioned by the manufacturer or NIJ during development.
Best-use practices are developed and passed on to other
agencies. For example, the police department in Cobb County,
Georgia, integrated the Time Domain Radar Vision TWS system
with its Peace Keeper SWAT vehicle. The department installed
the system on an articulated arm that can look through first-
or second-story walls. Video transmits to the interior of
the SWAT vehicle, allowing the viewer to remain in a safe
location. Such evaluations provide law enforcement with
hands-on use, the manufacturer with feedback on industry
needs, and NIJ with invaluable information in setting
research and development priorities for the future.
THROUGH-THE-WALL SURVEILLANCE: REDUCING RISK TO LAW ENFORCEMENT
Through-the-wall surveillance (TWS) technology could prove
invaluable to law enforcement officers, particularly in
high-risk situations involving hostages and barricaded
offenders (see main story). The 2005 FBI Uniform Crime
Report of Law Enforcement Officers Killed and Assaulted
(www.fbi.gov/ucr/killed/2005/killedsummaries.htm)
describes incidents in which TWS technology could have
aided responding officers and perhaps saved their lives.
Studying incidents like these provides insight into how
technology and revised practices can enhance officer safety.
- On January 19, 2005, the 42-year-old sheriff of the
Greenwood County Sheriffs Office (Kansas) was shot
and killed while attempting to execute an arrest warrant.
The sheriff, along with two deputies, arrived at a
residence where they encountered two people who said
that the subject of the warrant was not in the house.
The two deputies secured the outside of the house while
the sheriff, who had 26 years of law enforcement
experience, searched inside. While the sheriff was
standing near the staircase, the subject emerged from
his hiding place, placed a revolver to the sheriffs
chest, and fired twice.
- An officer with the Fort Worth Police Department (Texas)
was shot on November 29, 2005, while attempting to
arrest the alleged subject of a felony warrant. The
17-year veteran officer and two other officers arrived
at a residence where they thought the subject was staying.
A female met the officers at the door and told them
that the man for whom they were searching was not inside.
She invited the officers inside and gave them permission
to search the rooms. As the officers approached a
bedroom and opened the door, a man inside the room fired
at them. In the exchange of gunfire that followed, the
assailant shot the officer in the head. Two days later,
the officer died.
- A young female called the Newton Police Department (Kansas)
late on the evening of April 8, 2005, stating that her
mother was engaged in a domestic disturbance with the
mothers boyfriend, who was armed. ERT officials and
hostage negotiators arrived at the scene of the declared
hostage situation and established a perimeter barricade.
The suspect denied that he had any weapons and agreed
to a face-to-face meeting with the negotiators at the
door of the residence. As ERT personnel escorted two
negotiators, the suspect opened the front door, then
slammed it shut after the female inside said something
that angered him. Believing that the hostage was in
imminent danger, officers forced their way inside. The
suspect fired and mortally shot a deputy sheriff, the
first ERT official to cross the threshold. The suspect
then shot a detective, wounding him in the hands, arm,
and leg.
Return to text
Notes
NIJ does not exercise control over external Web sites. Read our Exit Notice.
[1] |
Law Enforcement
Officers Killed and Assaulted 2005, U.S. Department
of Justice, Federal Bureau of Investigation, October
2006: Tables 1, 20, and 65, available at
www.fbi.gov/ucr/killed/2005. |
[2] |
More information
on Radar Scope is available at
www.darpa.gov/sto/smallunitops/radarscope.html. |
[4] |
The FCC and the
American National Standards Institute set limits
for the safe amount of energy that can be emitted by
devices for the operator and the individuals under
surveillance. These limits are often not applied
when devices are used overseas, so many of the
companies sell a different, less-powerful version
in the United States. The FCC requirements also
ensure that the devices do not interfere with other
communications devices. |
[6] |
This device is
certified and complies with Part 15 of the FCC rules.
Parties using this equipment must hold a license
issued by the FCC to operate a transmitter in the
Public Safety Radio Pool under Part 90 of CFR Title 47. |
[7] |
Enhanced Tactical
Entry, ArmorOutlet.com, available at
www.armoroutlet.com/AOtactical/AOtac_radar.html. |
[8] |
More information
on the Xaver™ 800 is available at
www.camero-tech.com/xaver800.shtml. |
[9] |
The Lectric Law
Librarys Lexicon on Exigent Circumstances, Lectric
Law Library, available at
www.lectlaw.com/def/e063.htm. |
[10] |
Kruger, M.,
Transparent Urban Structures Enabling Capability
Program, Office of Naval Research, available at
www.onr.navy.mil/about/events/docs/83_TUS_Industry_Day_brief.pdf. |
[11] |
More information
on Visibuilding is available at
www.darpa.gov/sto/smallunitops/visibuilding.html.
See also Baranoski, E.J., Urban Operations: The
New Frontier for Radar, in DARPATech 2005 Conference
Proceedings, DARPA Special Projects Office, 2005,
available at
www.darpa.gov/darpatech2005/presentations/spo/baranoski.pdf. |
[12] |
For example, see
FY2007 Solicitation: Sensors and Surveillance
Technologies, available at
www.ncjrs.gov/pdffiles1/nij/sl000757.pdf. |