Evaluation of DNA recovery from improvised explosive device components after detonations

Abstract

Improvised explosive devices (IEDs) are commonly utilised by terrorist and criminal groups, and can be constructed using inexpensive and readily accessible materials. Despite the challenges posed by detonation, the DNA of those who made or placed the device may be recovered from the components of detonated IEDs. However, the recovered DNA is often scarce, degraded, damaged, and in the form of both cell-bound and cell-free DNA from, for example, skin contact. This study examines the recovery and the success of downstream analysis of DNA from various biological sources, including cell-bound blood and touch DNA and extracted cell-free DNA. DNA from different sources was deposited on different IED components with different surface materials. The IEDs were detonated using 40 g, 80 g, or 125 g of dynamite and DNA was sampled and analysed using real-time qPCR, STR analysis and mtDNA sequencing. The results indicated that multiple factors, including the type of DNA from different biological sources, dynamite weight, component type, DNA location and surface material, influenced the rate of successful genotyping. It was also demonstrated that the DNA quantities, and the success in STR profiling and mtDNA amplification were highly correlated for both cell-bound DNA and cell-free DNA. Moreover, sampling from internal phone components and PVC surfaces demonstrated higher DNA-typing success rates than DNA on external phone surfaces or metal-based components (SIM card holder, electrical wires, and circuit boards). DNA from blood revealed the highest rates of successful STR genotyping results across most detonated IED components, even for the highest weights of dynamite tested. Furthermore, mtDNA sequencing demonstrated a high success rate for low-template samples, even after the use of high amounts of explosive weight. A majority of DNA traces found on detonated IEDs are likely to consist of touch DNA from the production of the device. Here, the touch DNA samples on 9 V batteries yielded more DNA and higher success in DNA profiling than DNA on toggle switches and metal-containing electrical wires. These findings provide valuable insights into practical strategies for DNA recovery and analysis in IED-related forensic investigations.

Keywords: Forensic DNA analysis; Improvised Explosive Device; MtDNA sequence; STR; Trace DNA evidence.