Chemical traces - drugs, explosives, and gunshot residue

Motor vehicles are often used in the commission of crimes and are found in criminal activities, such as transporting drugs, explosives, and firearms. The detection of the presence of drugs, explosives, or Gunshot Residue (GSR) can represent very important evidence in the investigation of a crime. The three major classes of chemical traces described in this chapter could have some probative value in solving a crime: drugs, explosives, and gunshot residue. The chapter alludes to Ion Mobility Spectrometry (IMS) that is a highly sensitive analytical technique able to detect a wide range of chemical compounds (both organic and inorganic) at trace levels in the gas phase. Chemical traces can be sampled by using gas trapping technique, swabbing, vacuum lifting, or adhesive tape lifting. The chapter puts a view on the two levels of analysis for chemical traces: screening analysis and confirmatory analysis. Screening analyses are faster and cheaper than confirmatory analyses. However, screening analyses can give false-positive results, and should solely be conducted to avoid more expensive and time-consuming analysis of negative samples.