Evaluation of different sampling media for their potential use as a combined swab for the collection of both organic and inorganic explosive residues

Commercially available skin cleansing alcohol wipes and conventional swabs were investigated for their use as a universal sampling medium for the simultaneous collection of both organic and inorganic explosive residues. Six compounds with the potential to be encountered in casework [pentaerythritol tetranitrate (PETN), 2,4,6-trinitrotoluene (TNT), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), triacetone triperoxide (TATP), ammonium nitrate, and sodium chlorate] were selected as representative target compounds. Quantities of these target compounds were deposited on four different substrates (glass, plastic, aluminium foil and laminate). Two chosen alcohol wipes demonstrated better overall performance in the recovery of both the organic and inorganic representative compounds from each of the test surfaces compared to the results obtained using conventional cotton and polyester swabs, pre-moistened with various solvents, and a direct methanol wash (used as a control). Results obtained using dry cotton swabs indicated that it was not an effective swabbing system for the collection of both organic and inorganic explosive residues on common substrates.     

The sampling of ignitable liquids on suspects’ hands

In arson cases, the collection and detection of traces of ignitable liquids on a suspect's hands can provide information to a forensic investigation. Police forces currently lack a simple, robust, efficient and reliable solution to perform this type of swabbing.In this article, we describe a study undertaken to develop a procedure for the collection of ignitable liquid residues on the hands of arson suspects. Sixteen different collection supports were considered and their applicability for the collection of gasoline traces present on hands and their subsequent analysis in a laboratory was evaluated. Background contamination, consisting of volatiles emanating from the collection supports, and collection efficiencies of the different sampling materials were assessed by passive headspace extraction with an activated charcoal strip (DFLEX device) followed by gas chromatography–mass spectrometry (GC–MS) analysis. After statistical treatment of the results, non-powdered latex gloves were retained as the most suitable method of sampling.On the basis of the obtained results, a prototype sampling kit was designed and tested. This kit is made of a three compartment multilayer bag enclosed in a sealed metal can and containing three pairs of non-powdered latex gloves: one to be worn by the sampler, one consisting of a blank sample and the last one to be worn by the person suspected to have been in contact with ignitable liquids. The design of the kit was developed to be efficient in preventing external and cross-contaminations.     

Physical and chemical evidence remaining after the explosion of large improvised bombs. Part 2: Firings of calcium ammonium nitrate/sugar mixtures

Six test firings of large improvised explosive devices were carried out. The principal objectives of the firings were to measure the physical effects of the explosions upon representative objects placed nearby and to recover any chemical traces deposited on these objects. The results are intended for use as an aid in determining the approximate size and type of an explosive employed in terrorist attacks. Three 454 kg charges of a mixture of calcium ammonium nitrate (CAN) fertilizer and sugar, and three 2268 kg charges of a similar mixture, all confined in cylindrical steel containers were fired. Each charge was surrounded by 19 road signs mounted on posts and four vehicles, to act as witness materials. The analysis of aqueous swab extracts taken from the witness materials after firing showed the recovery of nitrate, ammonium and low levels of glucose. No sucrose was detected. Nitrate was usually recovered in greater quantities than ammonium and recovery generally decreased with increasing distance from the charges in any given direction. Quantities recovered from objects placed at the same distance in different directions varied considerably. Patterns of physical damage to the witness materials could be discerned according to their distance from the charge and the size of the charge. The velocities of detonation and air blast effects were measured.     

The impact of force,time, and rotation on the transfer of ammonium nitrate: A reductionist approach to understanding evidence dynamics

Empirical studies evaluating the conditions under which the transfer of forensic materials occurs can provide contextual information and offer insight into how that material may have been transferred in a given scenario. Here, a reductionist approach was taken to assess the impact of force, time, and rotation on the transfer of an explosive compound. An Instron ElectroPuls E3000 material testing instrument was used to bring porous and non-porous surfaces adulterated with an ammonium nitrate into direct contact with a human skin analogue, controlling for the force of contact, duration of contact, and rotation applied during contact. Quantifiable amounts of ammonium nitrate were recovered from all of the recipient surfaces demonstrating that ammonium nitrate is readily transferred from one surface to another, even when contact occurs for a short duration with a relatively low force. More particulates were transferred from non-porous surfaces onto the human skin analogue, but the amount of ammonium nitrate transferred did not depend upon the force of contact, duration of contact, or the amount of rotation applied. However, when contact occurred and involved rotation, a greater transfer of ammonium nitrate was observed, compared to those contacts occurring without rotation being applied. This approach complements more commonly-used holistic experiments that test multiple interacting variables in a realistic setting by isolating these variables, allowing them to be examined individually. This can be utilised to better understand the individual impact that specific variables have on the transfer of trace evidence in relevant crime reconstruction contexts.     

The Use of Adhesive Tape for Recovery of DNA from Crime Scene Items

Abstract: The selection of the appropriate method of collection of biological material from crime scene items can be crucial to obtaining a DNA profile. The three techniques commonly used for sampling items are: cutting, swabbing, and taping. The tape sampling technique offers an advantage, in that it enables the collection of a potentially highly informative source of DNA, shed epithelial cells, from selected areas on crime scene items (the inside fingers of a glove, for instance). Furthermore, surface collection of biological material by taping reduces co‐sampling of known PCR inhibitors such as clothing dyes. The correct choice of tape for crime scene item sampling is important. Not all tapes are suitable for biological trace evidence collection as well as DNA extraction. We report on one tape that met both these criteria. Three different cases are presented which demonstrate the usefulness of adhesive tape sampling of crime items. Finally, the advantages of the tape collection technique are discussed and guidelines for preferred areas of tape sampling on various casework items are presented.     

Trace analysis of urea nitrate by liquid chromatography-UV/fluorescence

In this paper we have adapted a technique, previously used to determine the presence of urea in aqueous samples of wine and urine, to detect trace levels of urea nitrate explosives. The procedure involves the reaction of the uronium ion (protonated urea) with a fluorophore, xanthydrol. By modification of the procedure to utilize non-aqueous reagents, in neutral conditions, it can be made specific to the presence of the urea nitrate ion pair. The procedure includes selective detection of derivatization products by UV and fluorescence following separation by High-Performance Liquid Chromatography (HPLC). Analytical method development included optimization of HPLC conditions (solvent, gradient), UV and fluorescence wavelengths, and derivatization parameters (xanthydrol amount, reaction times, temperature). The extraction of urea nitrate from surfaces was also investigated and optimized. For best quantification, it was shown that an internal standard was required; this resulted in a quantification limit around 0.17mM (21mg/L). The entire procedure could be performed in less than 30min per sample and potential interferences such as ammonium, nitrate, and urea did not produce a response under standard conditions.     

A Comparison of Solvent Extract Cleanup Procedures in the Analysis of Organic Explosives

The use of an organic solvent to extract explosive residues from hand swabs and postblast debris inevitably leads to the coextraction of unwanted materials, usually in far greater quantities than any explosive residue. In this study, the extraction efficiency of a number of solvent cleanup procedures including solid‐phase extraction (SPE), adsorbent resins such as Chromosorb‐104, and traditional materials such as silica and Florisil was calculated using a quantitative liquid chromatography–ultraviolet (LC‐UV) detection procedure. The Oasis^® HLB cartridge outperformed other cleanup procedures, with analyte recoveries approaching 95%, while the Amberlite XAD‐7 procedure returned the lowest overall recoveries. The matrix rejection ability of each method was then determined using a simulated highly contaminated matrix, with the adsorbent resins showing a higher degree of matrix rejection, which is seen as a reduction in background noise in the UV chromatogram using 210 nm detection.     

Trace analysis of urea nitrate in post-blast debris by GC/MS

Urea nitrate (uronium nitrate, UN) is an improvised explosive that looks very much like sugar and is easily made from accessible starting materials, urea and nitric acid. During the last decade it has been frequently used by terrorists in the Israeli arena and in other countries as well. It is difficult to identify urea nitrate in post-explosion debris, since only a very small fraction survives the blast. Also, in the presence of water, it readily decomposes to its original components, urea and nitric acid, two ubiquitous substances with relatively low evidential value. By further modifying McCord's recent version of Clark's method for the detection of minute amounts of urea, we were able to identify with high degree of certainty traces of uronium ion, the main characteristic factor of urea nitrate, in post-blast residues by GC/MS. The analytical process is based on the initial formation of xanthenyl urea by the reaction of uronium cation with xanthydrol, followed by reaction with alcohol to form xanthylurethane, which is readily identified by GC/MS. The reaction mechanism was corroborated by the use of labeled ¹⁵N-urea. By applying the technique to residues collected from scenes of controlled firing experiments, 4 out of 16 samples showed the presence of uronium cation as indicated by the formation of the corresponding xanthylurethane. Potential interferences such as urea and ammonium nitrate did not respond under standard conditions. However, under strongly acidic conditions (pH < 2), urea is converted into uronium ion, which is a nuisance, since it behaves as an authentic uronium cation. Such conditions, however, do not prevail at common crime scenes.     

The use of the M-Vac® wet-vacuum system as a method for DNA recovery

Collecting sufficient template DNA from a crime scene sample is often challenging, especially with low quantity samples such as touch DNA (tDNA). Traditional DNA collection methods such as double swabbing have limitations, in particular when used on certain substrates which can be found at crime scenes, thus a better collection method is advantageous. Here, the effectiveness of the M-Vac® Wet-Vacuum System is evaluated as a method for DNA recovery on tiles and bricks. It was found that the M-Vac® recovered 75% more DNA than double swabbing on bricks. However, double swabbing collected significantly more DNA than the M-Vac® on tiles. Additionally, it was found that cell-free DNA is lost in the filtration step of M-Vac® collection. In terms of peak height and number of true alleles detected, no significant difference was found between the DNA profiles obtained through M-Vac® collection versus double swabbing of tDNA depositions from 12 volunteers on bricks. The results demonstrate that the M-Vac® has potential for DNA collection from porous surfaces such as bricks, but that alterations to the filter apparatus would be beneficial to increase the amount of genetic material collected for subsequent DNA profiling. These results are anticipated to be a starting point to validate the M-Vac® as a DNA collection device, providing an alternative method when DNA is present on a difficult substrate, or if traditional DNA collection methods have failed.     

Recovery and detection of urea nitrate in traces

Urea nitrate (uronium nitrate, UN) is a powerful improvised explosive, frequently used by terrorists in the Israeli arena. It was also used in the first World Trade Center bombing in New York in February 1993. It is difficult to identify UN in postexplosion debris, because in the presence of water it readily decomposes to its original components, urea and nitric acid. A method for the recovery and detection of urea nitrate in traces is described. The residues are extracted with hot acetone, and the extract chromatographed on chromosorb G-HP. The eluent is analyzed by liquid chromatography mass spectrometry using atmospheric pressure chemical ionization (APCI). By applying this technique, we were able to identify urea nitrate in actual exhibits. It was found that UN can be also formed during the analytical procedure, by certain combinations of urea, nitrate ions, and a source of protons and, hence, the presence of the characteristic adduct ion does not necessarily indicate an "authentic" urea nitrate. Several solutions are suggested to overcome this ambiguity.     

Use of a commercially available hydrogel as a novel DNA surface sampling tool

A common requirement in the military, law enforcement, and forensic mission space is the need to collect trace samples from surfaces using a method that not only readily captures the sample but also retains its integrity for downstream identification and characterization. Additionally, collecting samples from three-dimensional objects (e.g., shell casings) is a challenge for which there is currently no validated standardized approach. Recently, hydrogels have been shown to have the potential for surface collection of trace bacterial spores, amino acids, and DNA. To test whether these hydrogels can serve as a viable collection medium for sampling DNA from surfaces, we carried out a series of preliminary tests examining collection efficiency and suitability of hydrogel material to recover samples of diluted, dried human DNA on a smooth polycarbonate surface. The recovery of surface DNA using a commercially available hydrogel was examined, and the efficiency compared to samples collected using a standard foam collection swab. DNA collected using the hydrogel and swab methods was then examined using quantitative polymerase chain reaction (qPCR) and short tandem repeat (STR) analysis to determine whether the collection material was compatible with these downstream processes. The hydrogel material used for this study collected the experimental DNA with comparable efficiency to standard collection swabs. In addition, qPCR and STR analyses demonstrated compatibility with the hydrogel collection and extraction process. These data suggest that hydrogels have the potential to be used as sample collection materials and deserve further characterization to elucidate their utility in collection from irregularly shaped, three-dimensional surfaces/materials.     

A Comparison of the Effectiveness of Swabbing and Flossing as a Means of Recovering Spermatozoa from the Oral Cavity

This study examined whether flossing the teeth is a more effective collection method in recovering spermatozoa than conventional swabbing techniques. It was hypothesized that inclusion of flossing as a collection method would extend the recovery of spermatozoa to longer postcoital intervals (PCIs). Eighteen individuals provided 174 oral cavity samples. Successful recovery of spermatozoa was assessed with respect to the collection method and reported activity in the oral cavity during the PCI. Samples were subjected to a differential extraction procedure prior to microscopic evaluation of the extracted pellet. The results indicate that swabbing is more effective than flossing when the PCI falls within 1.5–12 h. However, spermatozoa were recovered from seven floss samples where the corresponding swabs gave negative results. When combining the results from the two collection methods, the percentage of subjects from whom spermatozoa are recovered increases for each PCI beyond the 0‐h interval.     

LC-ESI-MS/MS法分析爆炸尘土中的硝化甘油

目的建立了高效液相色谱-质谱/质谱法（LC-ESI-MS/MS）测定尘土中的硝化甘油（NG）的方法,为日后测定爆炸残留物中的NG奠定基础。方法采用液液提取的方式提取样品,考察了前处理条件、色谱条件及质谱参数,最终确定实验方法。结果选择了最佳液相色谱质谱分析方法：固定相为SB C18（4.6×150 mm,5μm）,甲醇—0.05 mmol氯化铵做流动相,甲醇作提取溶剂;该方法在0.25～10 ng/g范围内呈良好线性,相关系数为0.9990;定量下限为0.25 ng/g;加标回收率为90.4%～95.2%。结论本方法操作简单,提取方便,有效避免了尘土复杂基质的干扰,结果准确可靠,灵敏度高,满足对爆炸残留物中硝化甘油的检测要求。     

Swabs as DNA Collection Devices for Sampling Different Biological Materials from Different Substrates

Currently, there is a variety of swabs for collection of biological evidence from crime scenes, but their comparative efficiency is unknown. Here, we report the results of an investigation into the efficiency of different swab types to collect blood, saliva and touch DNA from a range of substrates. The efficiency of extracting blood and saliva from each swab type was also tested. Some swabs were significantly more effective than others for sampling biological materials from different substrates. Swabs with the highest sampling efficiency, however, often did not have the highest extraction efficiency. Observations were recorded regarding practicality of each swab in a variety of situations. Our study demonstrates that selection of sampling device impacts greatly upon successful collection and extraction of DNA. We present guidelines to assist in evaluation of swab choice.     

The utility of polyester and cotton as swabbing substrates for the removal of cellular material from surfaces

Various types of cotton and polyester fabrics were tested to ascertain the optimal physical and chemical characteristics of fabrics needed for the removal of cellular material from surfaces. DNA quantitation values obtained on dried saliva stains showed no difference between cotton and polyester across all constructions and solvent conditions. Fabrics used dry and with water yielded higher quantitation values than those used with isopropanol. Quantitation values were also higher for wovens and nonwovens than knits across all solvent conditions. Low thread count fabrics used with water yielded higher quantitation values, but no correlation between thread count and quantitation values was observed with dry fabrics. A low thread count woven fabric, however, outperformed other tested fabrics when swabbing object surfaces in a highly used room. Full DNA profiles from fingerprints on glass surfaces were obtained with low thread count woven and nonwoven fabrics but not with the knit fabric tested.     

Comparison of the M-Vac® Wet-Vacuum-Based Collection Method to a Wet-Swabbing Method for DNA Recovery on Diluted Bloodstained Substrates*†‡

A wet-vacuum-based collection method with the M-Vac^® was compared to a wet-swabbing collection method by examining the recovery of diluted blood on 22 substrates of varying porosity. The wet-vacuum method yielded more total nuclear DNA than wet-swabbing on 18 porous substrates, recovering on average 12 times more DNA. However, both methods yielded comparable amounts of total DNA on two porous and two nonporous substrates. In no instance did wet-swabbing significantly recover more DNA. The wet-vacuum method also successfully collected additional DNA on previously swabbed substrates. Mitochondrial DNA yields were assessed, and outcomes were generally similar to the nuclear DNA outcomes described above. Results demonstrate that wet-vacuuming may serve as an alternative collection method to swabbing on difficult porous substrates and could potentially recover additional DNA on previously swabbed substrates. However, swabbing remains the preferred collection method on substrates with visible stains and/or nonporous surfaces for reasons of convenience, simplicity, and lower cost relative to the wet-vacuum method.     

Comparison of extraction methods for methamphetamine and its metabolites in tissue

Five extraction methods were examined for analysis of methamphetamine and its major metabolites in tissue samples. The extraction methods studied were an acetone extraction method, an ethanol extraction method, an ammonium sulfate method, dialysis, and a direct solvent extraction. Acetone, ethanol, and dialysis methods showed no interference from endogenous components using thin-layer chromatography and gas chromatography, and gave satisfactory recovery of methamphetamine, amphetamine, and p-hydroxymethamphetamine when added to rabbit liver. These methods, however, proved time-consuming. The ammonium sulfate method and direct solvent extraction method were simple and more rapid, but recovery of the polar metabolite was poor.     

Optimization of the collection and analysis of touch DNA traces

The aim of this work was to optimize a strategy for detection, collection, and analysis of touch DNA traces. 4N6FLOWSwabs™ and cotton swabs were compared by collecting touch DNA traces from glass slides and gun shell casings. Shed cells were visualized using Diamond™ nucleic acid dye and a digital fluorescent microscope. Different collection and extraction methods were tested. Collected samples were amplified with the AmpFlSTR® NGMSElect™ kit and the Precision ID mtDNA Whole Genome Panel.     

Physical and chemical evidence remaining after the explosion of large improvised bombs. Part 1: firings of ammonium nitrate/sugar and urea nitrate

Recent criminal acts in the United Kingdom, United States and other countries have demonstrated the dangers to public safety from the criminal use of improvised explosives on a large scale. Four sets of trials were carried out over four years, partly in collaboration with the United States Federal Bureau of Investigation, involving the firing of large bombs, mostly fertilizer based. The principal objectives of the firings were to measure the physical effects of the explosions upon objects representative of those that would be found at a real bomb scene and to recover any chemical traces deposited on these objects. The results are intended for use as an aid in determining the approximate size and type of an explosive employed in a terrorist attack. This paper describes the background behind the trials, the procedures for preparation of witness materials and charges, and the collection and analysis of physical and chemical evidence.     

Nondestructive Biological Evidence Collection with Alternative Swabs and Adhesive Lifters

In forensic science, biological material is typically collected from evidence via wet/dry double swabbing with cotton swabs, which is effective but can visibly damage an item's surface. When an item's appearance must be maintained, dry swabbing and tape‐lifting may be employed as collection techniques that are visually nondestructive to substrates' surfaces. This study examined the efficacy of alternative swab matrices and adhesive lifters when collecting blood and fingerprints from glass, painted drywall, 100% cotton, and copy paper. Data were evaluated by determining the percent profile and quality score for each STR profile generated. Hydraflock^® swabs, BVDA Gellifters^®, and Scenesafe FAST? tape performed as well as or better than cotton swabs when collecting fingerprints from painted drywall and 100% cotton. Collection success was also dependent on the type of biological material sampled and the substrate on which it was deposited. These results demonstrated that alternative swabs and adhesive lifters can be effective for nondestructive DNA collection from various substrates.