Detection of Pepper Spray Residues on Fabrics Using Liquid Chromatography-Mass Spectrometry

Abstract

Abstract The analysis of trace evidence for the presence of biological and nonbiological residues is an integral part of many criminal and civil investigations and the use of pepper spray self-defense weaponry by the general public, criminals, and law enforcement agents is increasing. Therefore, the possibility that pepper spray residues may be present as forensic evidence at crime scenes or from civil disturbances becomes more likely. We have investigated the effects of storage and washing on the detection of pepper spray residues (i.e., capsaicinoids) on cotton, cotton-polyester blend, wool, and nylon fabrics. The concentrations of the capsaicinoid analogues on the fabrics decreased between 5 to 60% during six months of storage when compared with samples of each fabric type that were prepared and analyzed at the onset of the stability study (Time 0). The rate of disappearance of the capsaicinoids was analogue specific. Degradation of the capsaicinoids was independent of fabric type and temperature of storage. We also investigated the effects of washing the fabrics on the detection of capsaicinoids. Fabrics were washed with water, 1% detergent, 1% bleach, or 5%Spray and Wash™. Water was the least effective method of removing the capsaicinoids from the fabric and bleach the most effective. Retention of the capsaicinoids on the fabrics following washing was affected by fabric type as well as the chemical properties of the individual capsaicinoid analogues. The uses and limitations of capsaicinoid residue evidence as an indicator of exposure to pepper sprays or use of pepper sprays are discussed.