3.0.c "Putting taggants in explosives and gunpowder will put bomb-making terrorists out of business."
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This article is from the talk.politics.guns Official Pro-Gun FAQ, by Ken Barnes (kebarnes@cc.memphis.edu) with numerous contributions by others.
3.0.c "Putting taggants in explosives and gunpowder will put bomb-making terrorists out of business."
see "Taggants in Explosives,"Congress of the United States, Office
of Technology Assessment, April 1980, SuDoc# Y3.T22/2:2Ex7 [This
report, now rather outdated, is also available in a summary version
with the SuDoc# Y3.T22/2:2Ex7/sum.]
Shanley, Agnes, ed., Harriston, Deborah with Roberts, Sandra,
"The Unmistakable Fingerprint of Taggants," "Chemical Engineering,"
v.103, p.35 (September 1996)
Wu, Corrina, "Tagged Out," "Science News,"v.150, pp.168-169
(September 14, 1996)
"Marking of products to establish identity and source,"
U.S. Patent #5,429,952 issued July 4, 1995 to Biocode, Inc.
Isotag LLC website at http://www.isotag.com/
National Academy of Sciences website at http://www.nas.edu/
"Marking, Rendering Inert, and Licensing of Explosive Materials,"
by Committee on Marking, Rendering Inert, and Licensing of Explosive
Materials, National Research Council, National Academy Press,
ISBN 0-309-05990-9, (1998)
In summary: The government-mandated addition of chemical "taggants"
to gunpowder and explosives has often been proposed in the U.S. as
a legislative strategy for combatting terrorist bombings, by giving
such potential bombmaking materials a unique chemical "signature"
which could provide investigators additional clues to work from in
identifying bombing suspects. Recent high-profile bombing incidents,
such as those at the Alfred P. Murrah Federal Building in Oklahoma
City, New York City's World Trade Center, as well as the Atlanta
Olympic Park bombing, and bombings at abortion clinics and elsewhere,
have given new political currency to the "taggant" issue, which was
last seriously debated by the U.S. government during the late 1970s.
As the public treatment of former Atlanta Olympic security guard
Richard Jewell shows, assigning blame for terrorist bombings is at
best an inexact science given current techniques, so the question
remains whether "taggants" will help or hinder the cause of justice
and public safety.
There are three technologies presently competing for the "taggant"
market, all of which are in current use in other products, primarily
to help identify counterfeit merchandise, such as bogus aircraft parts,
gasolines, cosmetics, medicines, and even alcoholic beverages. In
this role of assuring the quality and integrity of brand-name products,
these covert identification methods may in fact help save far more lives
than they ever could as additives to explosive materials. The earliest
"taggant" technology, originally developed at 3M, is the one most often
discussed when the issue is tagging explosives and gunpowder, since it
was the method under consideration in a 1980 report by the Congressional
Office of Technology Assessment. The "taggants" in this case are tiny
flecks of melamine plastic, which contain color coded layers sandwiched
between a magnetic film on one side, and a fluorescent layer on the other
side which glows under ultraviolet (UV) light. Detectives at a bombing
scene, the theory goes, would use UV light to find the glowing taggants,
collect them with a magnet, and read the color-coded layers under a
microscope to trace the serial number of the batch of explosive used
to make the bomb.
Another kind of tagging method uses biotechnology derived from the
immune systems of animals to detect the presence of specific chemicals
attached to a larger inert carrier molecule. The chemical tags, called
haptens, used in this method would only be identifiable by a specific
immune system molecule, a monoclonal antibody, developed to recognize
them. A microscopic plastic bead which had several different types
of haptens on its surface could be "read" by treating it with the
corresponding antibodies, in a similar manner to the way invading
bacteria and viruses are recognized as "foreign" by the immune system.
Determining which monoclonal antibodies could bind to the beads, and
which could not, would identify the haptens present on the bead, and
hence the code. The use of such a biological technique allows the
taggant particles to be made much smaller, and used and detected in
much lower concentrations than taggants using a color-code. Also, the
biotaggants would be difficult to remove from the explosive mixture,
and to identify, without the proper antibodies.
Lastly, there is a tagging system available which exploits the fact
that all the chemical elements can exist in the form of atoms having
different slightly different weights, called isotopes. Hydrogen,
for instance, can exist as "light" hydrogen, having only an electron
and a proton; and "heavy" hydrogen, which has an electron and a proton,
but also contains a neutron. (There is also a heavier radioactive
isotope of hydrogen, but such a radioactive tag, though easy to detect,
would not be ...technically suitable.) Both of these forms of hydrogen
are chemically very similar (almost identical), but can be distiguished
by using a sensitive piece of scientific equipment called a GC-mass spec
(short for gas chromatograph-mass spectrometer), which is capable of
weighing atoms and molecules. "Heavy" hydrogen atoms are much rarer
in nature than the "light" kind, so substituting particular "heavy"
hydrogen atoms for their "light" counterparts in some of the molecules
found in an explosive would not change the chemistry of the explosive,
but would create a unique pattern that is detectable using the proper
instruments, even when present at very low levels. Best of all, such
isotopically labeled explosives would not contain foreign materials
which might cause environmental and safety problems, the technologies
involved in making the tags are not easily duplicated, and the isotopes
themselves cannot be destroyed except by nuclear processes which would
also destroy whatever materials the tags are associated with.
Putting foreign "taggant" particles into explosives and gunpowder
is tricky and possibly very dangerous, and certainly useless for the
intended purpose if it can be easily defeated. The color-coded flecks
of magnetized plastic have several strikes against them. If they are
easy to find and remove from the bomb residue, they may be easy to
remove from the explosives beforehand. Treating gunpowder with a
magnet could pull them out of the mix. It has been proposed to include
some proportion of non-magnetic taggants, and/or conceal the fluorescent
layer with a substance that looks similar to the explosive itself, and
which would only reveal the fluorecence when it gets burned away in the
explosion, so as to make removing the taggants much more difficult.
However, unless the plastic particles are of similar size and density
to the powder, they could separate due to settling, or be screened out.
Settling out could cause changes in loading characteristics when powder
is used to manufacture ammunition. For instance, if the load is adjusted
to account for a certain proportion of taggant, the first part of a run
may be correct, but later, after settling, there may be rounds loaded
with high concentrations of taggant, and later still, rounds which are
overcharged with too much powder. The taggant itself might react
chemically with the highly reactive chemicals present in the powder
or explosive, with possibly destabilizing and dangerous results.
A 1980 report by the Congressional Office of Technology Assessment
noted possible instability resulting from the presence of high taggant
concentrations at high temperatures, though it's doubtful whether this
data has any relevance at the far lower concentrations in which the
taggants would ordinarily be used. If the taggants tend to clump, they
may become locally concentrated, however, causing ballistic inaccuracy.
If not degradable, microscopic bits of plastic taggants incorporated
into fertilizers, explosives and gunpowder would accumulate in the
environment, making it difficult to determine what taggants came from
where. Mixing several lots of tagged chemicals together as in a "home
brew" type improvised explosive, and/or diluting out or substituting
untagged chemicals for the tagged ones could defeat the system, or
reduce the concentration of the tags to levels indistinguishable from
the levels already present as a result of the use of explosives in
mining the components of many commonly used materials, such as concrete,
mortar, brick, and glass. The most powerful conventional explosives,
the so-called "fuel-air" explosives, would not be suitable for labeling
with such particles.
Even if the particles were reduced in size, as in the hapten
carrier molecules, it remains to be seen whether sufficient numbers
of the haptens on the surface of the carriers would retain the shapes
and chemical characteristics after an explosion which enable them to
be recognized by the highly sensitive monoclonal antibodies. Though
the hapten carrier tags would be tough to remove from the explosive,
and almost impossible to read without the proper antibodies, there
is still the possibility that the particles could react chemically
with the explosive, becoming unreadable, or causing destabilization.
There is also the possibility that the haptens could be chemically
modified in some fashion as to make them unreadable by the antibody,
in effect changing the chemical serial number present on the carrier,
either as a result of environmental exposure, or human intervention.
Treatment of the taggant particles with enzymes that destroy the
unique three-dimensional structure of the haptens without damaging the
explosive may be possible, depending upon their chemical properties.
Putting a protective coating on the hapten carrier particles might
prevent these problems, but it would probably also make the particles
more difficult for detectives to locate and read, increasing the
possibility of investigative errors. Again, substitution or dilution
of the tagged chemical could defeat the system, and there is also a
concern for accumulation in the environment. While the hapten carrier
tags have some advantages, such as increased security, they share many
of the drawbacks of the earlier color-coded plastic taggants, in that
they introduce a foreign particulate substance into the reaction mix.
As anyone who's cleaned a gun knows, there's always residue left
behind from incomplete combustion of the powder, so there is the
possibility that enough functional haptens can survive an explosion
to be useful to an investigation. But buildup of taggants inside a
gun might cause problems as well, and if foreign taggant particles
tend to cause ammunition to be less accurate, then using tagged
ammunition could put the user or bystanders at risk in defensive
situations where accurate shooting is critical.
Of all the current taggant technologies, isotopic labelling seems
to be able to overcome every possible objection, since no foreign
materials are being introduced into the powder or explosive, and the
infinitesimal differences at the atomic scale make no difference to
the performance of the chemicals they are included in. The isotopes
which are used in the process are naturally occurring, and though they
may accumulate locally for a while, they would gradually rejoin the
natural chemical cycles of the Earth, in the same manner as their
lightweight counterparts, with no adverse effect on organisms in the
environment. The added labor costs involved in cleaning up after each
batch of labeled explosive or powder so as not to cross-contaminate
later batches would be passed on to the consumer of all products in
which labeled substances are used, no matter what the taggant system.
Mining, and even agriculture (with labeling of ammonium nitrate like
that used in the Oklahoma City bomb) would be affected. And in
the case of gunpowder, which is often pre-blended at the factory to
achieve specific performance characteristics, with each lot being
distributed in small quantities to thousands of end users, the costs
could be substantial. Taggant evidence alone can't identify one
particular individual.
Finally, in response to a request by the U.S. Congress, the
National Academy of Sciences is currently studying the types and
use of taggants in explosives, with a final report due in February
1998. Whether the use of such technical evidence can make a difference
for justice in a sensationalized criminal case is today a matter of
substantial doubt, and that's a question no panel of distinguished
scientists can resolve. If jurors lack a basic scientific background
to evaluate the testimony of experts called upon to interpret the data,
they may just ignore what they don't understand, and all of the best
designed schemes for catching the bad guys will be for naught.
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