Application of a Modified 3D-PCSI-MS Ion Source to On-Site, Trace Evidence Processing via Integrated Vacuum Collection

Trace evidence, including hair, fibers, soil/dust, and gunshot residue (GSR), can be recovered from a crime scene to help identify or associate a suspect with illegal activities via physical, chemical, and biological testing. Vacuum collection is one technique that is employed in recovering such trace evidence but is often done so in a targeted manner, leaving other complementary, chemical-specific information unexamined. Here, we describe a modified 3D-printed cone spray ionization (3D-PCSI) source with integrated vacuum collection for on-site, forensic evidence screening, allowing the processing of targeted physical traces and nontargeted chemical species alike. The reported form factor allows sample collection, onboard extraction, filtration, and spray-based ionization in a singular vessel with minimal handling of evidence by the operator. Utilizing authentic forensic evidence types and portable MS instrumentation, this new method was characterized through systematic studies that replicate CSI applications. Reliability in the form of false positive/negative response rates was determined from a modest, user-blinded data set, and other attributes, such as collection efficacy and detection limit, were examined.

Chemical Analysis of Gunpowder and Gunshot Residues

The identification of firearms is of paramount importance for investigating crimes involving firearms, as it establishes the link between a particular firearm and firearm-related elements found at a crime scene, such as projectiles and cartridge cases. This identification relies on the visual comparison of such elements against reference samples from suspect firearms or those existing in databases. Whenever this approach is not possible, the chemical analysis of the gunpowder and gunshot residue can provide additional information that may assist in establishing a link between samples retrieved at a crime scene and those from a suspect or in the identification of the corresponding model and manufacturer of the ammunition used. The most commonly used method for the chemical analysis of gunshot residue is scanning electron microscopy with energy dispersive X-ray, which focuses on the inorganic elements present in ammunition formulation, particularly heavy metals. However, a change in the legal paradigm is pushing changes in these formulations to remove heavy metals due to their potential for environmental contamination and the health hazards they represent. For this reason, the importance of the analysis of organic compounds is leading to the adoption of a different set of analytical methodologies, mostly based on spectroscopy and chromatography. This manuscript reviews the constitution of primer and gunpowder formulations and the analytical methods currently used for detecting, characterising, and identifying their compounds. In addition, this contribution also explores how the information provided by these methodologies can be used in ammunition identification and how it is driving the development of novel applications within forensic ballistics.

[Current approaches for sampling to study the traces of gunshot residue]

An overview of researches, mainly by foreign specialists, on current available approaches for sampling to study the traces of gunshot residue (GSR) is presented. The comparative characteristics of traditional methods of samples (use of cotton and gauze tampons, blotting paper, textile fabrics, adhesive tapes, adhesives and vacuum samplers), as well as advanced technologies, including special devices and sorbents, are given. The characteristics of samplings from hands, scalp, nostrils, clothes of examined persons as well as procedures, that allow to increase the duration of GSR detection, are described in details. The importance of GSR sustainability over time is noted. On average, the most likely detection periods of particles are less than 1 hour for samples, collected from hands, more than 1 hour for samples from clothes and 2-3 hours for face. It is possible to detect the GSR particles in hair up to 24 h., and in nasal mucus after 6 h. of shot. The methods of identification and determination for analytes of inorganic and organic nature are discussed. The most common methods for determining heavy metal particles are atomic spectrometry, namely atomic absorption with electrothermal atomization and atomic emission. The combination of scanning laser ablation and mass-spectrometry with inductively coupled plasma makes it possible to detect more than 15 analytes in a single sample. Scanning electron microscopy with X-ray detectors is effective for the examination of powder particles. The described methods of sampling complement each other increasing the possibility of evidence base for court proceedings.

LC-MS/MS monitoring for explosives residues and OGSR with diverse ionization temperatures in soil & hands: 30 minutes for extraction + elution

A fast LC-APCI-MS/MS screening/confirmation method was developed and validated for trace analyses of 18 analytes which are explosives and organic gun shot residues including the challenging ones with diverse ionization conditions, in soil and on hands. (+) and (−) ionization modes were used after a single-step, low-volume solvent extraction procedure developed using methanol. Tape-lifting, stub, alcohol wipes, cotton bud were compared for collecting the residues from hands of a shooter. Tape-lifting and stub gave the highest recoveries and tape-lifting was chosen. Gradient elution system using ammonium chloride:methanol was developed. Whole procedure lasted approximately 30 min, was validated in both matrices, applied to real samples as post-blast residues, smokeless powder and the hands of a shooter, after shooting. Most of the recoveries were >80% and since all the precisions were <15%, quantitation was possible for all. Limit of Detection (LOD) and Limit of Quantification (LOQ) values were: 0.2–54.1 and 0.3–190.0 ngg−1 in soil, and 0.2–132.3 and 1.1–355.0 ngg−1 in tape-lift.

Gunshot residue detection technologies—a review

Background

Gunshot residue (GSR) is a shred of important trace evidence which helps forensic scientists solve a huge range of incidents related to firearms. The identification of the shooter to bullet identification from a gunshot wound help reconstruct a scene of the crime.

Main body

The review of this scientific paper is based on gunshot residue, its composition, and the growing advanced technology which allow us to study about how GSR analysis help to identify and detect residues. Various methods are acquired to identify and analyze organic and inorganic residues present when ammunition is fired. The review highlights the composition of GSR, its collection methods, and analysis part which emphasize on all the methods developed so far. The use of conventional methods including colorimetric and instrumentation-based analysis and advanced technology including electrochemical technique for detecting residues from the last 50 years. Spot tests or chemical tests were performed but they degrade the sample and can sometimes cause hindrance with some other nearby material present at the crime scene. Instrumentation techniques including AAS, ICP-MS, SEM, SEM-EDX, GC, HPLC, etc. are discussed in detail. Mostly advanced electrochemical methods developed are for inorganic gunshot residues (IGSR), but some researchers worked on both residues. Also, the fabricated electrochemical cells are replaced by a single strip-based technique for easy detection. So, to combat these issues, various scientists are moving towards sensor-based methods for rapid and reliable detection. These methods are more user-friendly, sensitive, and cost-effective and provide rapid detection results.

Conclusions

This review results in the composition of GSR, its collection methods, and analysis using sophisticated methods that emphasize all the methods developed so far and it also culminates the merits and demerits of all detection methods.

Non-destructive DNA recovery from handwritten documents using a dry vacuum technique

Investigations of many crimes such as robberies, kidnappings, and terrorism are often associated with the recovery of a paper document which has been written by the perpetrator. Paper can provide a variety of forensic evidence such as DNA, latent fingermarks, and indented writing. The focus of this study was DNA recovery from handwritten notes through a vacuum suction device while preserving the other evidence types and the integrity of the document. Copy paper was used to create handwritten documents and sheets with deliberate fingerprints, and indentations. The homemade vacuum device consists of a glass pipette blocked with a moistened swab and attached to a vacuum source. The method collected sufficient DNA amounts for DNA typing analysis with 80% of the 11 copy paper samples tested giving probative DNA profiles with five being eligible for DNA database entry. DNA recovery was also tested on other commonly encountered paper types. DNA quantities would have been sufficient for STR typing for approximately 50% of manila envelopes and notebook paper samples, but not for magazine pages and bank deposit slips. Deliberate sebaceous and eccrine latent fingermarks placed onto copy paper and developed with magnetic fingerprint developer or 1,2 indanedione were not affected by the vacuum swabbing technique. Simulated robbery notes with indented writing and processed using an Electrostatic Detection Apparatus (ESDA) demonstrated no interference through the DNA collection. This vacuum-based collection method enables laboratories to reverse the current questioned document workflow and start with DNA collection.

Applications of Direct Injection Soft Chemical Ionisation-Mass Spectrometry for the Detection of Pre-blast Smokeless Powder Organic Additives

Analysis of smokeless powders is of interest from forensics and security perspectives. This article reports the detection of smokeless powder organic additives (in their pre-detonation condition), namely the stabiliser diphenylamine and its derivatives 2-nitrodiphenylamine and 4-nitrodiphenylamine, and the additives (used both as stabilisers and plasticisers) methyl centralite and ethyl centralite, by means of swab sampling followed by thermal desorption and direct injection soft chemical ionisation-mass spectrometry. Investigations on the product ions resulting from the reactions of the reagent ions H₃O⁺ and O₂⁺ with additives as a function of reduced electric field are reported. The method was comprehensively evaluated in terms of linearity, sensitivity and precision. For H₃O⁺, the limits of detection (LoD) are in the range of 41-88 pg of additive, for which the accuracy varied between 1.5 and 3.2%, precision varied between 3.7 and 7.3% and linearity showed R² ≥ 0.9991. For O₂⁺, LoD are in the range of 72 to 1.4 ng, with an accuracy of between 2.8 and 4.9% and a precision between 4.5 and 8.6% and R² ≥ 0.9914. The validated methodology was applied to the analysis of commercial pre-blast gun powders from different manufacturers. Graphical Abstract.

Detection of Contact Traces of Powdery Substances

The current practice in securing the contact traces of chemical substances taken from clothes belonging to a person suspected of manual handling explosives is focused on pockets and cuffs. The outerwear worn by people who had contact with fluorescent powders that simulate explosives and drugs was the subject of this study. Clothes were first exposed to the test substance for a period of time and then analyzed by fluorescence methods to determine the location of the highest quantity of traces. The results obtained from the study confirm that the areas with the highest concentration of powdery traces are different from those suggested by current forensic practice. They appear to be promising for a more efficient identification of the suspects involved in illegal manufacturing of drugs of abuse or explosives. Moreover, they may be helpful for developing the methodology for handling the evidence material in the forensic clothing examination process.

Skin permeation of organic gunshot residue: implications for sampling and analysis

Traditional gunshot residue (GSR) analysis is based on detection of particulates formed from metals found in the primer. Recent concerns regarding the interpretation of GSR evidence has led to interest in alternatives such as the organic constituents (organic gunshot residue, OGSR) found in propellants. Previous work has shown OGSR to be detectable on hands for several hours after a firing event, and given the lipophilic nature of these compounds, it was expected that losses due to secondary transfer (an issue with GSR particulates) would be negligible. However, other loss mechanisms have been identified, specifically skin permeation and evaporation. This paper describes experimental and modeling studies used to elucidate characteristics of skin permeation of 5 compounds present in OGSR. Pharmaceutical methods were adapted to characterize skin permeation using a skin surrogate and Franz diffusion cells. The amount of compounds deposited on skin after an authentic firing event (1 and 2 shots) was experimentally determined and applied for the permeation experiments. A fully validated selected ion monitoring GC/MS method was developed for quantitative analysis, and easily accessible online tools were employed for modeling. Results showed that OGSR residues should be detectable on skin for many hours after a firing event of as few as one or two shots, with detection capability being a function of the efficacy of sampling and sample preparation and the instrumental method employed. The permeation rates of the OGSR compounds were sufficiently different to suggest the potential to develop methods to approximate time-since-deposition.

Analysis of gunshot residue and associated materials--a review

A comprehensive review of the scientific literature on gunshot residue (GSR) is presented. Aspects of both inorganic and organic GSR are discussed, from formation and distribution, to sample collection, preparation, and analysis using a variety of techniques. The interpretation of GSR results is also considered including issues surrounding the contamination, distribution, and transfer of GSR. Potential problems with ulterior sources of GSR like particles have been reported in the literature. For example, particles from environmental and occupational sources have been highlighted as exhibiting similar chemical and morphological characteristics to GSR. These findings are put into context with regard to interpreting samples. A move toward a "case by case" approach is argued to be more preferable to a "formal" classification system where possible. The analysis of both inorganic and organic compositions of residue samples as well as morphological considerations is considered to be a more ideal approach to GSR analysis, wherever practicable.

SEM/EDS analysis and characterization of gunshot residues from Brazilian lead-free ammunition

The exposition to heavy metal-rich airborne due to fire practicing has forced to the development of heavy metal-free environmental ammunition primers all over the world. Here we characterize the GSR elements present in the Brazilian lead-free ammunition produced by Companhia Brasileira de Cartuchos (CBC) and commercialized by MagTech in the U.S. and Europe under the name CleanRange centerfire cartridges. Both first and second generations of CleanRange in calibers 9 mm Luger, .40 S&W, .380 AUTO and .38 SPL were analyzed and compared to regular Brazilian CBC ammunition by scanning electron microscopy/energy dispersive spectroscopy. Differences in composition and morphology of GSR particles from the two generations of CleanRange were observed. The first generation ammunition (found in Europe) presented spherical particles, being strontium the only unique element detected. The second generation (found in the U.S.) produced irregular particles composed mostly by potassium, aluminum, silicon and calcium. We can conclude that identification of GSR derived from CBC second generation lead-free ammunition in suspects' hands may be impossible without the addition of a distinct metallic taggant in the primer composition by the manufacturer.

Development of a Quantitative LC-MS/MS Method for the Analysis of Common Propellant Powder Stabilizers in Gunshot Residue

In traditional scanning electron microscopy/energy dispersive X-ray analysis of gunshot residue (GSR), one has to cope more and more frequently with limitations of this technique due to the use of lead-free ammunition or ammunition lacking heavy metals. New methods for the analysis of the organic components of common propellant powder stabilizers were developed based on liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). A multiple reactions monitoring scanning method was created for the screening of akardite II, ethylcentralite, diphenylamine, methylcentralite, N-nitrosodiphenylamine, 2-nitrodiphenylamine, and 4-nitrodiphenylamine, present in standards mixtures. Five out of seven of these target compounds can be selectively identified and distinguished from the two others with a high accuracy. Samples from the hands of a shooter were collected by swabbing and underwent solid phase extraction prior to analysis. Detection limits ranging from 5 to 115 mug injected were achieved. Results from several firing trials show that the LC-MS/MS method is suitable for the detection of stabilizers in samples collected following the firing of 9 mm Para ammunitions.

Detection of gunpowder stabilizers with ion mobility spectrometry

This study is the first reported ion mobility detection of ethyl centralite and diphenylamine (DPA) smokeless gunpowder stabilizers, together with the nitroso and nitro derivatives of diphenylamine. First, the applicability of the ion mobility spectrometry (IMS) for the substances of interest was determined. The existence of numerous peaks, both in positive and negative modes, clearly demonstrates the success of these experiments. All mono and di-nitro derivatives of DPA tested were detected with this method. Unfortunately, many of the ions generated were not accurately identified. However, reduced mobility constants representative of each ion generated under defined operating conditions could be used for purpose of compound identification. The method was then successfully tested on real gunpowder samples. By the use of IMS, we managed to establish a rapid, simple and sensitive screening method for the detection and identification of smokeless gunpowder organic components.

A Novel Method for the Analysis of Discharged Smokeless Powder Residues

A novel method for the estimation of intermediate-long firing distance range is proposed. The method is based on the characterization and chemical analysis of the smokeless powder particles on the target. An adhesive lifter is applied to collect the suspected gunshot residues (GSRs) from the surface of an object, and a Modified Griess Test (MGT) is carried out after alkaline hydrolysis on the adhesive lifter. Visualized particles are removed from the adhesive lifter under a microscope. Two systems are used for the analysis of organic discharge residues from the smokeless powder: (1) gas chromatography/thermal energy analysis (GC/TEA) for the analysis of nitroglycerine (NG) and 2,4-dinitrotoluene (2,4-DNT), (2) gas chromatography/mass spectrometry (GC/MS) for the identification of organic components such as DNT, NG, and some stabilizers. By using this procedure and confirming that the suspected particles are indeed GSR, one can estimate the intermediate-long firing distance of c. 0.75-3 m in the presence of very few particles and provide information for the classification of ammunition type in casework.