Forensic Discrimination of Smokeless Powders Using Carbon and Nitrogen Isotope Ratios

Improvised explosive devices pose a threat to the public by way of terrorism and criminal activities. In the United States a commonly used low explosive in improvised explosive devices is smokeless powder (SP), due to its ease of access. Traditionally, forensic examinations are often sufficient in determining the physical and chemical characteristics of SPs. However, these exams are limited in differentiating or associating SPs when comparing two materials which are physically and/or chemically consistent. Stable isotope analysis of carbon and nitrogen has been used for explosives to further forensic chemical comparisons and aid in sample differentiation. In this manuscript we explore the utility of stable isotope analysis of SPs to differentiate manufacturer and geographic origin. Both bulk isotope analysis and component isotope analysis of carbon and nitrogen via an extraction method using dichloromethane were evaluated to compare the overall isotope signature of individual SPs. Through the combination of bulk and component isotope measurements of SPs, we were able to identify geographic relationships; however, the manufacturer origins were not as clearly discriminated. This technique demonstrates a potential improvement to traditional forensic examinations of smokeless powder by adding additional information when explosives are chemically and/or physically consistent.