AFTE Store - CHLORINDAZON DS: An Improved Reagent for the Detection of Trace Amounts of Copper

For the past 30 to 40 years, American forensic scientists working in the firearms and/or trace evidence sections of crime laboratories have typically employed the dithiooxamide (DTO) reagent for the detection of copper around the margins of suspected bullet holes and suspected bullet impact sites. Although specific for copper, the DTO reagent produces a dark, dingy greenish-gray response that is often difficult to see against background colors and other residues that frequently
transfer to filter paper ‘lifts’. An alternate reagent, well-known in several European forensic laboratories and which has some improved properties, has become available in United States. The reagent is called Chlorindazon DS and its chemical name is 1-(6-chloroindazole-3-yl-azo)-2-hydroxynaphthalene-3,6-disulfonic acid, disodium salt. This reagent has an additional advantage in that it also produces a stable color complex with zinc- an element in certain heavy, metal-free,
primer compositions and at least one brand of frangible bullets. The procedures and test results presented here provide an introduction to the potential uses and application for this ‘new’ reagent in those cases where the presence of copper around the margin of a bullet hole, in a suspected bullet impact site, and/or in close-range gunshot residue deposits are of potential forensic importance.