Recovery of DNA and fingermarks following deployment of render-safe tools for vehicle-borne improvised explosive devices (VBIED)

The influences of dusty environments on the STR typing success of post-detonation touch DNA samples

As the use of improvised explosive devices (IEDs) in a broad spectrum of offences continues, it is vital that research is performed to assess the capabilities of the forensic DNA profiling technology currently available to provide information as to potential perpetrators. This work investigates some of the most important gaps in our understanding surrounding the poor success rates in DNA profiling obtained through the sampling of touch DNA on post-detonation IED samples. It has been previously suggested that the use of Diamond™ Nucleic Acid Dye may fix cells to a surface, therefore reducing the effect of an experimental process to remove or damage those cells. This was found not to be the case for samples undergoing a detonation as there was no difference in the resultant post-detonation profiles between the stained samples, stained prior to detonation, and unstained samples. The comparison of data from previously performed research, within an enclosed explosives chamber, to real-world outdoor detonation events in a rural and dusty environment was investigated. It was found that there was a significant difference between the environments for the aluminium but not for the battery or electrical tape substrates indicating that environment has the potential to influence STR success through the introduction of PCR inhibitors; humic acid within rural natural dust was introduced here. No difference was observed in cell loss due to the detonation between environments and the dirt within the PCR was higher in the 'outdoor' samples. The effect on cellular retention and damage due to the sample's distance from the charge has been thoroughly investigated through incremental 100 mm exposure. Distance from the charge was found to affect every metric analysed; these being the cell loss from samples, the number of alleles amplified in resultant direct PCR profiles, and the total RFU of the subsequent profiles. These data outline the importance of this work allowing results to be assessed and triage decisions be made accordingly. The analysis of wood, PVC pipe, a mobile phone with rubber buttons, a SIM card, and a circuit board showed that none of these samples at 400 mm from the charge caused substrate specific PCR inhibition. On-site collection teams do not need to triage collection based on these sample types as there was no significant difference observed in their ability to return DNA profiling data. Surface area and inhibitor presence are key variables to consider when determining STR processing workflow for post-detonation samples as for samples with larger surface areas within the outdoor environment PCR post-extraction is preferential to direct PCR.

Influence of ink and smoke ATM security systems on dactyloscopy and subsequent DNA analysis after detonation

Automated Teller Machine bombings are an increasing societal problem that are often committed using Improvised Explosive Devices. The evolution in IEDs and the negative consequences for society require new security measures to prevent these crimes. Ink staining and security smoke devices are added to cash cassettes, in order to protect ATMs and prevent ATM bombings. Traces found at crime scenes, such as fingerprints and DNA, can contribute to the identification of perpetrators. However, the effect of ink staining and security smoke devices on dactyloscopy and DNA profiling is still unknown. In the current study, we demonstrate that procedures using Citrus Cleaner or sulfosalicylic acid were successful in removing ink and security smoke deposited on plastic plates but did result in the massive loss of fingerprint information as only a low number (4%) of good quality fingerprints were recovered after smoke contamination. Secondly, security ink Sun Blue ES2, but not SICPA Green and Sun Blue ES1, had a significant impact on DNA profiling success. DNA concentrations obtained from blood spiked swabs decreased with increasing ink concentration resulting in a complete loss of genotype information with the addition of ≥10 μl Sun Blue ES2. No noticeable PCR inhibition or DNA degradation was detected during quantification, but a decreased efficiency of DNA extraction could not be excluded. Security smoke, on the other hand, does not seem to have a significant influence on DNA analysis. Precautions must therefore be taken in order to avoid contaminating DNA swabs with ink during sampling. Thirdly, only a single negative impression of a glove in ink and a single glove print were able to be visualized with white fingerprint powder on detonated cash cassettes. In conclusion, the detection of glove prints and fingerprints is limited and security ink, contrary to smoke, after detonation can have a negative influence on downstream DNA analysis procedures.

Blast Suppression Foam, Aqueous Gel Blocks, and their Effect on Subsequent Analysis of Forensic Evidence

In addition to having blast mitigation properties, aqueous foam concentrate AFC-380 blast suppression foam is designed to capture aerosolized chemical, biological, and radioactive particles during render-safe procedures of explosive devices. Exposure to aqueous environments and surfactants may negatively affect forensic evidence found at the scene, but the effects of AFC-380 foam and aqueous gel on the preservation and subsequent analysis of forensic evidence have not previously been investigated. Sebaceous finger and palm prints and DNA samples on paper, cardboard, tape, and various metal and plastic items, along with hairs, carpet and yarn fibers, and inks and documents, were exposed to AFC-380 foam. Similar mock evidence was also exposed to a superabsorbent gel of the type found in aqueous gel blocks used for shrapnel containment. Exposure to foam or aqueous gel was associated with a dilution effect for recovered DNA samples, but quality of the samples was not substantially affected. In contrast, exposure to AFC-380 foam or gel was detrimental to development of latent finger and palm prints on any substrate. Neither the hair nor the fiber samples were affected by exposure to either the foam or gel. Indented writing on the document samples was detrimentally affected by foam or gel exposure, but not inks and toners. The results from this study indicate that most types of forensic evidence recovered after being exposed to aqueous gel or blast suppression foam can be reliably analyzed, but latent finger and palm prints may be adversely affected.

Survival of forensic trace evidence on improvised explosive devices: perspectives on individualisation

Improvised Explosive Devices (IEDs) are weapons of modern times, used by terrorist groups and thereby causing substantial damage to communities. There is a widespread misconception that destructive conditions like heat, water or pressure destroy all forensic evidence. Moreover, the plausibility to detect identifiable fingermarks and DNA on components of IEDs is insufficiently known. Therefore, this study investigated the effects of neutralisation and explosion on latent fingerprints and touch DNA. In a majority of the cases, comparative fingermark- and DNA testing resulted in individualisation. In some cases, despite extremely low amounts of contact DNA detected after deployment of render-safe tools or detonation, full STR profiles could be constituted, even after applying fingerprint development techniques. This research shows that latent fingerprints and touch DNA on improvised explosives can be successfully detected after destructive conditions and possibly be linked to the perpetrators of such crimes. This individualising power offers perspectives to enhance forensic investigations of terrorism-related crimes.

The rotary zone thermal cycler: a low-power system enabling automated rapid PCR

Advances in molecular biology, microfluidics, and laboratory automation continue to expand the accessibility and applicability of these methods beyond the confines of conventional, centralized laboratory facilities and into point of use roles in clinical, military, forensic, and field-deployed applications. As a result, there is a growing need to adapt the unit operations of molecular biology (e.g., aliquoting, centrifuging, mixing, and thermal cycling) to compact, portable, low-power, and automation-ready formats. Here we present one such adaptation, the rotary zone thermal cycler (RZTC), a novel wheel-based device capable of cycling up to four different fixed-temperature blocks into contact with a stationary 4-microliter capillary-bound sample to realize 1-3 second transitions with steady state heater power of less than 10 W. We demonstrate the utility of the RZTC for DNA amplification as part of a highly integrated rotary zone PCR (rzPCR) system that uses low-volume valves and syringe-based fluid handling to automate sample loading and unloading, thermal cycling, and between-run cleaning functionalities in a compact, modular form factor. In addition to characterizing the performance of the RZTC and the efficacy of different online cleaning protocols, we present preliminary results for rapid single-plex PCR, multiplex short tandem repeat (STR) amplification, and second strand cDNA synthesis.