The Physical Effects of Contact and Close‐Distance Gunfire on Sweatshirt Fleece

Powder stippling caused by the impact of propellant particles during close‐distance gunfire has been previously described on skin and solid objects only. Additionally, radial tearing has been described as clear evidence of a contact‐distance shot, requiring no further testing. Patterns of discrete perforating holes (referred to here as “stippling perforations”) and other physical damage on sweatshirt fleece fabrics were prepared. Using the firearm and ammunition in this study, stippling perforations were observed to a maximum muzzle‐to‐target distance of 35 cm (10 inches). In addition, radial tearing and disintegration were present (and often more extensive) at greater than contact distance. The presence of stippling perforations could augment muzzle‐to‐target distance estimates generated using the Griess test, or allow distance estimates when the Griess test is not feasible. Unlike what has been previously reported, testing on the original evidence (or similar substitute) is warranted when physical damage is used to estimate shooting distance.     

The Analysis of Gun‐Cleaning Oil as Long‐Distance Gunshot Residue and Its Implications for Chemical Tags on Bullets

Using a BB gun, it was shown that a gun‐cleaning oil (GCO) can be wiped from the barrel by a projectile and carried much longer distances than those usually associated with solid gunshot residue (GSR). Analysis of GCO subsequently deposited on a target was performed using pentane extraction and gas chromatography. (Hoppe's GCO was used here as a model.) When a 0.45 caliber handgun was used, analysis reveals that most of the GCO wiped from the barrel does not survive, owing to the elevated temperatures encountered. However, two components of the GCO, a long‐chain fatty acid and its ethyl ester, do survive and can be detected in the bullet wipe. This suggests that GCO may be considered as GSR, uniquely detectable at long distances, and that other chemical compounds could either be added to a GCO or directly to bullets, to serve as identifying chemical tags.     

Evaluation of Total Nitrite Pattern Visualization as an Improved Method for Gunshot Residue Detection and its Application to Casework Samples

Visualization of nitrite residues is essential in gunshot distance determination. Current protocols for the detection of nitrites include, among other tests, the Modified Griess Test (MGT). This method is limited as nitrite residues are unstable in the environment and limited to partially burned gunpowder. Previous research demonstrated the ability of alkaline hydrolysis to convert nitrates to nitrites, allowing visualization of unburned gunpowder particles using the MGT. This is referred to as Total Nitrite Pattern Visualization (TNV). TNV techniques were modified and a study conducted to streamline the procedure outlined in the literature to maximize the efficacy of the TNV in casework, while reducing the required time from 1 h to 5 min, and enhancing effectiveness on blood‐soiled samples. The TNV method was found to provide significant improvement in the ability to detect significant nitrite residues, without sacrificing efficiency, that would allow for the determination of the muzzle‐to‐target distance.     

A Study of Background Levels of Antimony,Barium, and Lead on Vehicle Surface Samples by Graphite Furnace Atomic Absorption

Law enforcement agencies routinely sample for gunshot residue (GSR) by bulk techniques and often submit swabs taken from other surfaces besides the hands of the suspect shooter. This study aims to establish the prevalence of antimony, barium, and lead on normally handled automobile surfaces by graphite furnace atomic absorption analysis. No positives were determined on 50 sampled automobile surfaces above cutoff (positive) from background levels. Transfers of GSR particles from shooter hands to automobile surfaces were found to potentially allow for positive GSR determinations, but such transfers seem to be dependent on the shooting conditions and length of GSR exposure. We determined that our bulk analysis method yields an overall 87.94 ± 5.52% extraction efficiency from cotton swabs, while the LOQ determinations strengthening the fact that bulk analysis methods are valid and valuable tools for GSR investigations.     

Controversial Suicide Case Using a Submachine Gun with a Sound Suppressor—The Need of Team Work of Forensic Chemistry and Firearm Examiners

Evidence materials in a presumed suicide case were studied by a firearm examiner and a forensic chemist. The victim's body with double gunshot wounding in his forehead, a machine gun in the sustained fire mode with a silencer, and four cartridge cases were found. Examinations of the evidence, the case file studies, and experiments dedicated to the case were carried out. Relationships between the placement of cartridge cases and the gun were established using a fast camera. The distributions of gunshot residues on the evidence materials and within the comparative gunshot patterns were studied by means of optical and electron microscopy, X‐ray microanalysis, and infrared spectroscopy. The shooting distance was assessed to be 30 cm or more, whereas the greatest distance that could have been achieved by the victim himself was about 11–13 cm. The obtained results supported the version of homicide rather than suicide.     

A versatile technique for the investigation of gunshot residue patterns on fabrics and other surfaces: m-XRF

With heavy-metal-free ammunitions becoming more and more popular, it is necessary to find methods to visualize patterns of those elements in gunshot residues (GSRs) that are not accessible by chemographic coloring tests. The recently introduced millimeter-X-ray fluorescence analysis (m-XRF) spectrometer Spectro Midex M offers an easy way to record mappings of GSRs containing such elements in order to determine shooting distances as well as the general composition of these particles. A motorized stage enables samples of a maximum size of 20 x 20 cm to be investigated, like fabric, clothes, adhesive tapes (Filmolux films), and polyvinylalcohol gloves of shooter's hands. Human tissues can be measured using a Peltier-cooled specimen holder that is mounted onto the stage. As the spot size of the exiting X-rays lies in the millimeter range, which is adequate for the assessment of the residue patterns for shooting distance determination, a significant reduction in measurement time is achieved compared with mu-XRF methods. Test shots with heavy-metal-free ammunitions were performed on different target materials, like pork skin and fabric, and the elemental distributions of Ti, K, and Ga were determined. In order to show the capability of the spectrometer for conventional lead ammunitions as well, a shot series of 5-100 cm shooting distance and an adhesive tape of a shooter's hand were investigated analogously. A comparison of several methods applied in GSR investigation shows the advantages of the m-XRF method.     

Utilization of X‐ray Computed Tomography for the Exclusion of a Specific Caliber and Bullet Type in a Living Shooting Victim

A bystander claimed to have been shot by a police officer, and CT scans were used to match qualitative and quantitative aspects of the unremoved bullet with police issued 9 mm Luger ammunition. CT scan methodology proved a valid approach for the measurement of bullets based on calculated measurement capability and correlation with “gold standard” physical measurement by vernier caliper. Measurements regarding length and base diameter, as well as length/diameter ratio, were insufficient to unambiguously identify a specific caliber, or a bullet of specific mass within a caliber class. It was, however, possible to exclude a bullet of specific design and mass with well‐characterized precision and accuracy values under selected CT scan conditions. A 9 mm Luger bullet (115 gr FMJ RN) was excluded from involvement in a shooting based on qualitative bullet shape combined with length, base, and ratio measurements of the bullet in‐situ for the victim.     

A Study of the Presence of Gunshot Residue in Pittsburgh Police Stations using SEM/EDS and LC‐MS/MS

Due to possible secondary transfer of gunshot residue (GSR) onto a suspect in police custody prior to sampling, a baseline must be created for the amount of GSR present. With an increase of “lead free” ammunition, testing for both gunpowder and primer GSR is relevant. Seventy samples were collected using carbon‐coated adhesive stubs from four Pittsburgh Police Stations and vehicles to investigate these locations as sources of secondary GSR contamination. These seventy samples were analyzed for primer GSR using scanning electron microscopy‐energy‐dispersive X‐ray spectrometry. One primer GSR particle was detected; no sample was classified as positive for primer GSR. These same samples were then analyzed for gunpowder GSR using liquid chromatography coupled to tandem mass spectrometry to test for akardite II, ethylcentralite, diphenylamine, N‐nitrosodiphenylamine, 2‐nitrodiphenylamine, and 4‐nitrodiphenylamine. Ethylcentralite was quantifiable in two test samples. These results suggest there is a negligible potential for secondary transfer of primer and gunpowder GSR.     

Preparation of a Ytterbium‐tagged Gunshot Residue Standard for Quality Control in the Forensic Analysis of GSR

Preparation of a ytterbium‐tagged gunshot residue (GSR) reference standard for scanning electron microscopy and energy dispersive X‐ray spectroscopic (SEM‐EDS) microanalysis is reported. Two different chemical markers, ytterbium and neodymium, were evaluated by spiking the primers of 38 Special ammunition cartridges (no propellant, no projectile) and discharging them onto 12.7 mm diameter aluminum SEM pin stubs. Following SEM‐EDS microanalysis, the majority of tri‐component particles containing lead, barium, and antimony (PbBaSb) were successfully tagged with the chemical marker. Results demonstrate a primer spiked with 0.75% weight percent of ytterbium nitrate affords PbBaSb particles characteristic of GSR with a ytterbium inclusion efficiency of between 77% and 100%. Reproducibility of the method was verified, and durability of the ytterbium‐tagged tri‐component particles under repeated SEM‐EDS analysis was also tested. The ytterbium‐tagged PbBaSb particles impart synthetic traceability to a GSR reference standard and are suitable for analysis alongside case work samples, as a positive control for quality assurance purposes.     

Analyzing the Dynamics and Morphology of Cast‐off Pattern at Different Speed Levels Using High‐speed Digital Video Imaging

During a bloodstain pattern analysis, one of the essential tasks is to distinguish between different kinds of applied forces as well as to estimate their level of intensity. In this study, high‐speed digital imaging has been used to analyze the formation of cast‐off patterns generated by a simulated backswing with a blood‐bearing object. For this purpose, 0.5 mL blood was applied evenly over the last 5 cm of a blade simulant. Bloodstains were created through the controlled acceleration of a backswing at different speed levels between 1.1 m/sec and 3.8 m/sec. The flight dynamics of blood droplets were captured with an Olympus^® i‐Speed 3 high‐speed digital camera with a Nikon^® AF Nikkor 50 mm f/1.8 D lens and analyzed using the Olympus i‐Speed 3 Viewer software. The video analysis showed that, during the backswing, blood droplets would move toward the lower end of the knifepoint and would be tangentially thrown off. These droplets impacted on the horizontal surface according to the arc of the swing. An increase in velocity led to longer cast‐off patterns with distinct morphological characteristics. Under laboratory conditions, bloodstain pattern analysis allows certain conclusions about the intensity of a backswing and provides instructions on the position of the offender. However, due to the number of unknown variables at a crime scene, such interpretation of cast‐off patterns is extremely limited and should be performed with extreme caution.     

Dating of Iron Gall Ink Using the Dissolution‐Diffusion Method

In many criminal and civil cases, some questioned documents are written with iron gall ink. Determining the date when an iron gall ink entry was written can be important to assess the authenticity of a document. A dissolution‐diffusion method was successfully employed to draw aging curves of iron gall ink entries stored in controlled conditions over 40 months. Calibration curves were created to indicate the relationship between the average dissolution‐diffusion rate of ink components and the age of ink entries stored under natural aging conditions. As preliminary findings of this study, the mixed solution of dimethyl formamide (DMF) and anhydrous ethanol was suitable to dissolve the dye of iron gall ink strokes made at different time. It was also determined that brands of iron gall inks, types of paper, and thickness of iron gall ink strokes had varying impacts on estimating the dates of iron gall ink strokes.     

Implementation and Validation of the Teleshake Unit for DNA IQ™ Robotic Extraction and Development of a Large Volume DNA IQ™ Method

Abstract: Automated platforms used for forensic casework sample DNA extraction need to be versatile to accommodate a wide variety of sample types, thus protocols frequently need modification. In this study, DNA IQ? methods previously developed for the Biomek^® 2000 Automation Workstation were adapted for the Teleshake Unit using normal volumes and all deepwell extraction, and a large volume DNA IQ? method developed. DNA purification without detectable contamination of adjacent reagent blanks is reported in the extraction of tissue samples containing several micrograms of DNA. Sensitivity and contamination studies demonstrated similar performance with the manual organic extraction method for bloodstain dilution samples. Mock casework samples demonstrated the effectiveness of the Teleshake and Teleshake large volume methods. Because of the performance and increased versatility of the DNA IQ? extraction with these modifications, the Teleshake Unit has been implemented in both normal and large volume automated DNA extractions at the Virginia Department of Forensic Science.     

Development of a Real‐Time PCR‐Based Method for Analyzing Semen‐Specific Unmethylated DNA Regions and Methylation Status in Aged Body Fluid Stains

The detection of semen in forensic investigation is considered important evidence of sexual assault. In this study, we report the development of a real‐time polymerase chain reaction‐based method for identifying semen that can simply and rapidly analyze the semen‐specific unmethylated region of the DACT1 gene. Using two fluorescent probes designed for the methylated or unmethylated status, this method could perform quantitative analysis of the methylation status in this region. Furthermore, this method was used to analyze various body fluid samples, including 29‐year‐old semen and blood stains. The results showed that this method can detect almost exclusively semen or nonsemen signals even in highly decomposed samples, while a few semen or nonsemen samples showed slight signals of the other fluorescence probe. Although there is still a need for further analysis such as setting thresholds to analyze unknown samples, this method could be a useful supplementary tool for identifying semen, especially in old stains such as those in cold‐case investigations.     

Preliminary Studies on the Absorbance Ratio Method Used to Determining the Age of Stamp‐pad Ink Seal

Stamp‐pad ink seals are often placed on important documents, and determining the dating of stamp‐pad ink seal is important to assess the authenticity of a document. In this study, 20 different brands and types of stamp‐pad inks were classified by ultraviolet visible spectrophotometer. Six different brands and types of papers were classified by micro‐Fourier transform infrared spectrometer and visual spectral comparator 6000. Three different brands of stamp‐pad inks and two different types of paper were used to make diachronic samples of the seals. A method was employed to date the stamp‐pad seals by comparing absorbance ratios and inks of known age. Curves were created to show the relationship between the absorbance ratio of ink and the age of the seals. The experimental results showed that the absorbance ratio method was applicable for the relative dating of stamp‐pad ink seals in some cases where the seal was placed on the document within 10 weeks.     

Evaluation of a Headspace Solid‐Phase Microextraction Method for the Analysis of Ignitable Liquids in Fire Debris

The chemical analysis of fire debris represents a crucial part in fire investigations to determine the cause of a fire. A headspace solid‐phase microextraction (HS‐SPME) procedure for the detection of ignitable liquids in fire debris using a fiber coated with a mixture of three different sorbent materials (Divinylbenzene/Carboxen/Polydimethylsiloxane, DVB/CAR/PDMS) is described. Gasoline and diesel fuel were spiked upon a preburnt matrix (wood charcoal), extracted and concentrated with HS‐SPME and then analyzed with gas chromatography/mass spectrometry (GC/MS). The experimental conditions—extraction temperature, incubation and exposure time—were optimized. To assess the applicability of the method, fire debris samples were prepared in the smoke density chamber (SDC) and a controlled‐atmosphere cone calorimeter. The developed methods were successfully applied to burnt particleboard and carpet samples. The results demonstrate that the procedure that has been developed here is suitable for detecting these ignitable liquids in highly burnt debris.     

A Computational Framework for Age‐at‐Death Estimation from the Skeleton: Surface and Outline Analysis of 3D Laser Scans of the Adult Pubic Symphysis

In forensic anthropology, age‐at‐death estimation typically requires the macroscopic assessment of the skeletal indicator and its association with a phase or score. High subjectivity and error are the recognized disadvantages of this approach, creating a need for alternative tools that enable the objective and mathematically robust assessment of true chronological age. We describe, here, three fully computational, quantitative shape analysis methods and a combinatory approach that make use of three‐dimensional laser scans of the pubic symphysis. We report a novel age‐related shape measure, focusing on the changes observed in the ventral margin curvature, and refine two former methods, whose measures capture the flatness of the symphyseal surface. We show how we can decrease age‐estimation error and improve prior results by combining these outline and surface measures in two multivariate regression models. The presented models produce objective age‐estimates that are comparable to current practices with root‐mean‐square‐errors between 13.7 and 16.5 years.     

Next‐Generation Sequencing of the Bacterial 16S rRNA Gene for Forensic Soil Comparison: A Feasibility Study

Soil has the potential to be valuable forensic evidence linking a person or item to a crime scene; however, there is no established soil individualization technique. In this study, the utility of soil bacterial profiling via next‐generation sequencing of the 16S rRNA gene was examined for associating soils with their place of origin. Soil samples were collected from ten diverse and nine similar habitats over time, and within three habitats at various horizontal and vertical distances. Bacterial profiles were analyzed using four methods: abundance charts and nonmetric multidimensional scaling provided simplification and visualization of the massive datasets, potentially aiding in expert testimony, while analysis of similarities and k‐nearest neighbor offered objective statistical comparisons. The vast majority of soil bacterial profiles (95.4%) were classified to their location of origin, highlighting the potential of bacterial profiling via next‐generation sequencing for the forensic analysis of soil samples.