Bombing incidents, particularly at the World Trade Center in New York in 1993, the Alfred P. Murrah Federal Building in Oklahoma City in 1995, and the Centennial Olympic Park in Atlanta in 1996, have increased calls for federal legislation requiring the inclusion of chemical tags, or taggants, in materials that can be used to produce explosives. Such taggants also could be included in black and smokeless powder for the identification of gun users. National Rifle Association (NRA) officials have expressed their skepticism regarding the use of taggants, arguing on the basis of a 1980 study that such additions could destabilize gunpowder. The Antiterrorism and Effective Death Penalty Act of 1996 originally contained a provision to fund a six- month study of taggants to be conducted by the Treasury Department. However, the NRA and other organizations lobbied successfully to exclude gunpowder from the study.
In the early 1970s, Richard G. Livesay developed the first tags, which were tiny particles approximately a tenth of a millimeter in diameter consisting of layers of colored melamine plastic, a chemically inert substance likely to survive an explosion. Distinctive layering permits identification of the manufacturer, the production date, and the distributor of the explosive. Fluorescent materials included in the taggant assisted in detection. The magnetized taggants, when placed over a magnet, reveal their unique color coding. This type of taggant, called Microtaggant, is produced by Microtrace, a company that sells its product primarily to Switzerland, where since 1980 all explosives have been tagged. From 1984 to 1996, the Swiss used Microtaggants to solve over 500 bombing cases.
More recently, researchers have developed another type of taggant--nonradioactive heavy-isotope variations of molecules already present in the explosives. These isotopes of hydrogen, carbon, nitrogen, and oxygen vary only in atomic weight from materials already in the explosive. Potentially millions of distinct codes can be written as identifiers of specific explosive compounds. Identifying the tags requires relatively sophisticated laboratory analysis. Two companies, Microtrace of Minneapolis, Minnesota, and Isotag of Houston, Texas, provide isotope tags for many business firms for such products as shampoo, paint, gasoline, perfume, and glue to protect brand name products from counterfeiting and dilution. Taggant producers enthusiastically recommend the use of their products for those materials employed in the production of explosives, such as flammable liquids, black powder, smokeless powder, fireworks powders, ammonium nitrate fertilizer, and fuel oil.
Manufacturers demonstrate less enthusiasm for taggants. The Institute of Makers of Explosives contends that the inclusion of