Detecting Concealed Weapons: Directions for the Future
by Chris Tillery
About the Author
Mr. Tillery is the associate deputy director for science
and technology at the National Institute of Justice.
On July 24, 1998, a man entered the U.S. Capitol building
in Washington, DC, with a .38-caliber handgun concealed
under his clothing. A security check point with a portal
weapons-detection system had been established at the
entrance of the building. Knowing that his gun would be
detected if he walked through the portal, the man stepped
around it. Immediately, he was confronted by Jacob Chestnut,
one of the Capitol Police officers operating the portal.
The man drew his gun and killed Chestnut. He then shot and
killed a second officer, John Gibson, before he was
stopped.[1]
Seven years later, on December 5, 2005, a man with a bomb
vest under his clothing approached a shopping mall in Netanya,
Israel. His behavior alerted police and mall security. When
he was confronted outside the mall, the suicide bomber
detonated his bomb, killing 5 people and injuring
50.[2]
Although there has yet to be a suicide bombing in this country,
such an attack could happen anywhereon a bus, at a
mall, at the Super Bowl, or at the Academy Awards. It is
vital for law enforcement to be able to detect and respond
to weapons at a sufficient distance to allow officers to
make decisions and take actions that deal safely with the
situation. For over a decade, the National Institute of
Justice (NIJ) has been working to address this need.
Limitations of Current Weapons-Detection Systems
The incident at the U.S. Capitol showed the limitations of
current security-detection portal systemsthey must
be near an individual to work. They generally provide
sufficient warning when it comes to detecting a knife,
but they cannot detect weapons that can kill beyond arms
reach. By the time a handgun or a bomb vest is detected,
it generally is too close to be dealt with safely.
But there are ways to provide more warning. One is to move
the portal farther from the operator. For example, it can
be incorporated into a buildings entrance and operated from
a control room at another location. A person who wants to
enter the building is then required to first go through the
portal before an interior door opens to allow admittance to
the building. If the portal detects a weapon, the operator
does not open the interior door or the door locks
automatically, without the operators intervention. To
further protect the public, exterior doors open only after
a second interior door is closed behind the person who has
entered. In this way, only one person at a time can enter
the building, preventing the possibility that innocent
bystanders would be trapped in an entryway with an armed
person.
Despite their advantages, remote portal weapons-detection
systems have significant limitations. They require more
space for the remote location, which is not always available,
and they impede traffic flow. Using a remote exterior door
with screening equipment and a second interior door in a
crowded venue, such as a sporting event or an airport,
would impede the flow of pedestrian traffic and cause
people to collect in a relatively small area, creating a
prime target for a suicide bombing or other attack.
Another approach to detecting concealed weapons is through
the use of back-scatter x-ray weapons-detection systems,
which use low-dose x-rays to develop images of objects
under clothing. The x-rays pass through clothing and are
reflectedor scattered backby the skin. These
systems have the same limitation as existing portal
weapons-detection systems: They require close proximity
to detect a weapon. They can, however, reduce the nuisance
alarms that occur when metal objects other than weapons
are detected and thus move pedestrian traffic more quickly
through security checkpoints.
Where Are We Going?
In the late 1990s, NIJ launched an aggressive program to
find ways to detect concealed weapons from a safe distance.
The Institute investigated a wide range of potential
solutionsradar, infrared radiation cameras, acoustic
devicesand determined that passive millimeter wave
(MMW) cameras offered the greatest potential.
A passive MMW camera is one that does not use an artificial
source of MMW radiation. It develops images from ambient
MMW radiation, which, like infrared radiation, is all
around but cannot be seen by the human eye. Although both
infrared and MMW radiation can penetrate clothing to develop
images of hidden objects, MMW radiation is more effective
in this respect. For example, an MMW camera can develop
an image through a heavy coat, but an infrared camera cannot.
Over the past decade, NIJ has leveraged research and
development on MMW technology performed by the U.S.
Department of Defense to the point that there now are
commercially available MMW weapons-detection
cameras.[3] These
cameras represent a 10-fold decrease in size and cost
from the initial prototypes, but much work remains to be
done in improving resolution and range, and reducing weight
and cost.
NIJ continues to work on developing the potential for MMW
technology to detect concealed weapons. For example, the
Institute is exploring the use of automobile
collision-avoidance MMW radar; and in another project, it
is supporting efforts to develop smaller, less expensive MMW
cameras. NIJ is also reexamining other technologies, such
as infrared cameras, that have advanced in the last decade
and could offer new opportunities for the detection of
concealed weapons.
New Technologies Demand New Protocols
New technology is never, in itself, the solution. Rather,
the solution lies in adopting effective policies and
practices for use of the technology. Emerging weapons-detection
technologies pose complex questions for law enforcement
agencies, particularly the development of legally defensible
protocols for using them.
For instance, using a device to remotely search people
walking in a public venue, without their knowledge, raises
fundamental Fourth Amendment concerns with respect to
lawful searches. When and under what circumstances can
such a device be used? What is the publics reasonable
expectation of privacy in a public venue? What constitutes
probable cause for the use of these devices? What is a
reasonable search?
Another issue is appropriate use-of-force protocols. The
use of deadly force is governed by the totality of the
situation. There are two salient points to keep in mind
when developing protocols under these circumstances. The
first is that no technology is perfect. An MMW camera may
reveal an object that, in all likelihood, is a bomb vest,
but there is still a possibility, however slim, that it
may not be a bomb vest. The second point is that a suicide
bomber, by definition, intends to kill or injure as many
people as possible. Use-of-force protocols for dealing
with a person armed with a handgun, who may or may not be
suicidal, may not be appropriate for dealing with a suicide
bomber, whose device might be detonated remotely by an
accomplice or by the bomber himself even after being
restrained.
Under the Nations federalist system of government, the
development of specific protocols for the effective use of
these technologies must be done jurisdiction by jurisdiction.
Jurisdictions need not work in a vacuum, however. Key
professional public safety organizations have begun to
develop guidelines, including ways for responding to
suicide bombers. The International Association of Chiefs
of Police (IACP), for example, includes this issue in its
Training Key monographs, which provide officers with
authoritative information on a broad variety of law
enforcement practices and procedures. For more information
on the IACP Training Key monographs, see
www.iacp.org Exit Notice.
A New Century of Challenges
The new century brings with it new challenges in detecting
concealed weapons. As criminal justice professionals work
on the technology and protocols to address these challenges,
NIJ will continue to provide the research and development
that the Federal, State, and local law enforcement communities
need to help prevent attacks and ensure the safety of citizens.
NCJ 219608
Notes
NIJ does not exercise control over external Web sites. Read our Exit Notice.
[1] |
Shooting at the
Capitol, Special Report: From the Shootings to the
Investigation, Washington Post, available at
www.washingtonpost.com. |
[2] |
Myre, G. Bomber
Kills 5 Outside Shopping Mall in Israel, New
York Times, December 5, 2005, available at
www.nytimes.com. |
[3] |
Two commercially
available products resulting from NIJs investment
in concealed-weapons detection are the Sago ST 150
(www.trexenterprises.com/Subsidiaries/sago.html)
and the Brijot BIS-WDS
(www.brijot.com).
These products and manufacturers are cited for
informational purposes only and do not constitute
product approval or endorsement by the National
Institute of Justice. |