Morphological and chemical profiling for forensic hair examination: A review of quantitative methods.

Within the past two decades, there have been many studies for quantitative analysis on human hair samples. Microscopical and chemical analysis techniques have been used to analyze various aspects of hair regarding biological, chemical, anthropological, cosmetic, and forensic applications. Studies have attempted to develop quantification methods to increase the evidentiary value of hair in forensic casework. The literature reviewed in this paper provides some of the current techniques used for forensic examinations and quantitative methods. Although microscopical analysis has been scrutinized in the past, using chemical and microscopical techniques can provide a myriad of information. The extraction of DNA from hair provides high-value evidence; however, it may not be readily available and may yield inconclusive results. Hair analysis can be used for many forensic applications such as comparison, toxicology, and exposure analysis. In this article, we will review published research material regarding chemical and microscopical techniques for human hair analysis. Aspects considered for this review were the sample size requirement for analysis and the destructive nature of the instrumental method. This review will focus on both macro and micro quantitative methods for human hair analysis.

A brief study on the effects of storage conditions on sexual lubricant components in the presence of a biological fluid.

This study illustrated the effects of environmental conditions (i.e., temperature) on the components of a condom lubricant in the presence of vaginal secretion. Understanding the effects of storage is important for the short-term handling of sexual assault kits, that may contain post-coital swabs, prior to chemical analysis. This preliminary three-day investigation utilized gas chromatography-mass spectrometry (GC-MS) to analyze the samples at three timepoints (24, 48, and 72 h). Lubricated and non-lubricated swabs were exposed to five storage conditions. After percent recovery calculation, GC-MS interpretation, and statistical analysis, it was determined that storing swabs at room temperature (22 °C) for up to 72 h best maintained the integrity of the sexual lubricant - in comparison to T0 - as opposed to colder storage temperatures of 4 °C and - 20 °C. Despite the varying degree of changes in the storage conditions and temperatures, PDMS components were persistent in all lubricated samples and can be used to confirm the presence of condom lubricant if initially present in the sample.

Discrimination of white automotive paint samples using ATR-FTIR and PLS-DA for forensic purposes.

The consequences of a hit-and-run car crash are significant and may include serious injuries to the victims, health system overload and even victim's death. The vehicle and driver identification are often challenging for local law enforcement. The aim of this study was to develop a methodology to discriminate between automotive paint samples according to the make of the vehicle and its color shade. 143 white samples (collected at traffic accident scenes) were analyzed in situ by Fourier transform infrared spectroscopy with attenuated total reflectance (ATR-FTIR) and coupled microscopy. Principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA) were performed for data analysis. The samples were split into three groups: calibration set, validation set and external test set. The figures of merit were calculated to assess the quality of the model. Sensitivity, specificity, and efficiency rates were, respectively, 98,9%, 98.4% and 98.6%, for the calibration set. For the validation group, the classification accuracy was 100%. Correct classification rates for the internal validation set and external test set were 100% and 79.1% respectively. The technique is clean, fast, relatively low-cost, and non-destructive. Damaged regions of the samples were avoided by using the attached microscope. Limiting the age of the samples to a maximum of 10 years was enough to avoid misclassifications due to the natural degradation and weathering of the sample. Since the external test group is formed by underrepresented classes, its correct classification rate (79.1%) can be potentially improved at any time, by including and analyzing more samples.

A longevity study to determine appropriate storage conditions for sexual lubricants using spectroscopic and spectrometric techniques.

There has been an increase in the number of reported cases in which assailants have used a condom or sexual lubricant. Sexual predators understand that DNA from seminal fluid is one of the main forms of evidence used to connect a suspect to a victim or crime scene; therefore, the use of condoms in sexual assault cases has increased. This dilemma has led to research into other types of trace evidence (e.g., sexual lubricants). The study presented herein was performed to determine the optimal storage time length and conditions appropriate for storing trace lubricant residue. This research project used Fourier transform infrared spectroscopy (FTIR), direct analysis in real time-high resolution mass spectrometry (DART-HRMS), and gas chromatography-mass spectrometry (GC-MS) techniques to analyze the stored swabs containing sexual lubricants at 8 timepoints over 18 months. Blank, personal lubricant, and condom swabs were stored under several environmental conditions. Swab storage allowed for the determination of whether lubricants degraded, thus adversely affecting the ability to recognize the classification patterns. Resulting spectra from each instrument can be used to identify environmental degradation of lubricant samples and generate investigative leads. Pearson Correlation Coefficients and time plots of the chemical components were used to determine if chemical breakdown occurred for each lubricant and if the pattern changed significantly. Results showed that the strongest correlations occur between the initial timepoint (T 0) and one month (T1m), with correlations decreasing consistently up to eighteen months (T18m). The best storage conditions were determined to be 22 °C at both 16% and 50% humidity. The ability to understand the effects of environment and time to the analysis of sexual lubricants may offer helpful information when analyzing sexual assault kits.

Analysis of hair color and texture for forensic examinations.

Efforts have been conducted to evaluate hair features empirically, for example, color; however, a review of current literature showed few studies investigating cortical texture analysis. The development of high-resolution digital microscopes allows researchers to obtain more accurate measurements of hair features. In this study, digital microscopy was used to explore variance within the cortical texture, color, and density characteristics throughout hair strands. In this study, 20-25 naturally shed hairs from 12 individuals of different ancestries were collected. Measurements of three different features were collected: entropy texture measurements, that is, measurement of the randomness of pigment granules and cortical fusi; color distributions of the hairs via a red-green-blue (RGB) color model; and the calculation of the pigment density ratio using hue-saturation-value color model. Analysis of variance was performed on data collected from each analysis type to assess inter- and intra-person variability. The F-ratios obtained, which compares inter-person to intra-person variability, ranged from 9.29 to 69.24. Cortical texture and color measurements showed promising results in differentiating between inter-person samples. Although density ratios showed the least potential for discrimination, it provided another level for differentiating inter-person hair samples. The location that provided the best differentiation of strands from different donors could be made at a 20.0 mm distance from the strand's proximal end for all three features measured. The methods proposed in this study show the potential to quantify hair features that exhibit better differentiation of hair from different individuals.

SEM-EDS analysis and characterization of glitter and shimmer cosmetic particles.

Perpetrators are often aware of commonly used trace evidence in forensic casework, thereby limiting potential transfer during a crime. With the lack of common evidence left behind at a crime scene, consideration of alternative potential evidence is necessary. Glitter and shimmer particles from cosmetic products will potentially transfer from or onto an offender, crime scene, or victim. The transfer of these cosmetic particles during a close personal attack generally goes unnoticed, and thus offenders are unaware of the use of such evidence that may associate a suspect to a crime scene. In this study, 36 glitter and 40 shimmer samples were analyzed using scanning electron microscopy - energy dispersive X-ray spectroscopy (SEM-EDS) whereby characterization schemes were developed to help identify particles potentially transferred during close personal assaults. Samples were classified into 7 glitter and 4 shimmer groups based on elemental composition, and the developed classification models showed high potential to accurately associate or differentiate unknown cosmetic particles collected from a potential crime scene, with cross-validation accuracies ranging from 94 to 100%. Pearson results showed no overlap between inter- and intra-sample correlations, thereby suggesting low possibility of false sample identification. Analysis of variance with post-hoc Tukey test was subsequently performed to determine how well detected elements and element peak ratios differentiated the glitter and shimmer samples, respectively.

Correction to: Temperature-Dependent DART-MS Analysis of Sexual Lubricants to Increase Accurate Associations.

Near the end of fifth paragraph in the Introduction, an equation in the next to last sentence should read.

Temperature-Dependent DART-MS Analysis of Sexual Lubricants to Increase Accurate Associations.

The analysis of lubricant evidence is a recent development in sexual assault investigations and in the absence of any biological evidence may assist in linking an assailant to the victim or crime scene. An ambient ionization technique, high-resolution direct analysis in real-time mass spectrometry (HR-DART-MS), was employed to characterize a sample set of 33 water-based lubricants. As lubricants are complex multicomponent mixtures, this study investigated if different thermal desorption temperatures could elucidate different additives and provide additional information. A low-temperature, high-temperature, and thermal desorption/pyrolysis DART-MS protocol was used to characterize the water-based lubricant sample set. The strength of the methodologies was evaluated using positive and negative likelihood ratios that were calculated from inter- and intra-pairwise comparisons using Pearson correlation coefficients. The low-temperature DART-MS protocol afforded valuable information pertaining to volatile additives (e.g., flavors and fragrances) and provided positive likelihood ratios that would provide strong support for true positive and negatives than the high-temperature protocol when associating between individual samples and samples to their respective sub-groupings. The thermal desorption/pyrolysis DART analytical protocol provided enhanced differentiation between samples due to the precise temperature control using a thermal gradient. Moreover, the total ion spectra obtained from the thermal desorption/pyrolysis protocol, not only had high positive and negative likelihood ratios, this method also provided the most discrimination as determined by empirical cross entropy plots. Graphical Abstract.

Analysis and classification of smokeless powders by GC-MS and DART-TOFMS.

Partially burned smokeless powder particles may be present as a form of evidence following a shooting or explosive event, such as the explosion of a pipe bomb. The characterization and classification of residual smokeless powers may allow for a known sample, i.e. sample collected from a suspect, to be connected to an unknown sample, i.e. sample obtained from a crime scene. In this study, thirty-four (34) smokeless powders were analyzed using GC-MS and DART-TOFMS to determine how comparable the discriminatory power of each instrument was based on the smokeless powder constituents identified within each sample. Analysis of smokeless powders by DART-TOFMS generated comparable results to GC-MS in a fraction of the time (∼30seconds). Most peaks observed between the instruments were the same; however, N-nitroso-DPA was only observed in the DART-TOFMS spectra but was not a significant contributor. Samples were naturally grouped together using hierarchical cluster analysis and principal component analysis, based on underlying features in the resulting spectra. Samples were placed into groupings based on significant peaks observed and relative intensities. Classification models were presented for both GC-MS and DART-TOFMS and subsequently tested and compared. The classification models used in this study were linear discriminant analysis, k-nearest neighbors, and random forest modeling. The groups observed were similar between the two instruments, indicating that DART-TOFMS provides comparable data to GC-MS and could be used as a rapid screening technique.

DART-MS: A New Analytical Technique for Forensic Paint Analysis.

Automotive paint evidence is one of the most significant forms of evidence obtained in automotive-related incidents. Therefore, the analysis of automotive paint evidence is imperative in forensic casework. Most analytical schemes for automotive paint characterization involve optical microscopy, followed by infrared spectroscopy and pyrolysis-gas chromatography mass spectrometry ( py-GCMS) if required. The main drawback with py-GCMS, aside from its destructive nature, is that this technique is relatively time intensive in comparison to other techniques. Direct analysis in real-time-time-of-flight mass spectrometry (DART-TOFMS) may provide an alternative to py-GCMS, as the rapidity of analysis and minimal sample preparation affords a significant advantage. In this study, automotive clear coats from four vehicles were characterized by DART-TOFMS and a standard py-GCMS protocol. Principal component analysis was utilized to interpret the resultant data and suggested the two techniques provided analogous sample discrimination. Moreover, in some instances DART-TOFMS was able to identify components not observed by py-GCMS and vice versa, which indicates that the two techniques may provide complementary information. Additionally, a thermal desorption/pyrolysis DART-TOFMS methodology was also evaluated to characterize the intact paint chips from the vehicles to ascertain if the linear temperature gradient provided additional discriminatory information. All the paint samples were able to be discriminated based on the distinctive thermal desorption plots afforded from this technique, which may also be utilized for sample discrimination. On the basis of the results, DART-TOFMS may provide an additional tool to the forensic paint examiner.

Determining the effects of adulterants on drug detection via enzyme-linked immunosorbent assay and adulterant tests strips.

The use of immunoassays for drug screening has increased due to their sensitivity towards target analytes, specifically the enzyme-linked immunosorbent assay (ELISA) technique. Adulterant test strips are commonly used in conjunction with immunoassay tests to ensure the integrity of the specimen has not been altered prior to drug screening. This research focuses on determining which adulterants can produce a false negative result, not only with 1 of the screening tests, but throughout the entire screening process. Seven adulterants were tested for their ability to generate false negative results for the ELISA by decreasing the detectable antigen concentration to below industry-used cut-off levels. Each adulterant was added to a urine sample containing 1 of 5 different drugs at 5 different concentrations (0, 5, 10, 25, and 50%). Five different urine samples that contained drugs and drug metabolites of benzoylecgonine, THC-COOH, α-PVP, D-amphetamine, and Diazepam, were treated with each of the 7 adulterants and analyzed on the ELISA and subsequently by 2 different test strips. The results indicated that 4 adulterants (ie, bleach, Drano®, vinegar, and sodium nitrite) generated the most false negatives for both test strips and the ELISA at surprisingly low concentrations, ~5% v/v. Thus indicating that there are still ways that a urine sample that contains drugs could be analyzed and labeled "clean and free of drugs" after going through a common screening process. These results suggest that new drug screening techniques need to be developed to detect adulterants in urine samples for drug screening.

Determining the effect of cartridge case coatings on GSR using post-fire priming cup residue.

Ammunition is typically composed of a lead-based priming mixture which contributes to the characteristics most commonly used for the identification of gunshot residue (GSR). Due to the health risks often associated with lead, the use of lead-free primers in ammunitions is becoming more popular. Thus, the presence of GSR is becoming more difficult to discern based on the traditional means, i.e. the presence of lead (Pb), barium (Ba), and antimony (Sb). While research has been conducted on the differences between lead-based and lead-free muzzle discharge residue, few have researched other components of ammunition which may lead to other means of characterizing GSR. This research, therefore, covers that gap by focusing on the priming cup present in ammunition and the residue which may originate from it, that can contribute to muzzle discharge residue. In this study, a lead-based and a lead-free ammunition from four different manufacturers were chosen. The cartridges were fired using a Glock 17, 9mm Parabellum, collected post-fire, and subsequently de-primed resulting in the removal of the anvil. The GSR present on the anvils and cups was analyzed using scanning electron microscopy coupled with energy dispersive x-ray spectrometry (SEM-EDX). The data was then processed using unit vector analysis for normalization and analyzed using principal component analysis (PCA) and linear discriminant analysis (LDA). This data was then used to determine the components of the cartridge case which contribute to GSR and develop a method of characterization between lead-free and lead-based ammunition. Such a method will improve the detection of GSR by strengthening the criteria of identification.

Chemical discrimination of lubricant marketing types using direct analysis in real time time-of-flight mass spectrometry.

RATIONALE: In comparison to other violent crimes, sexual assaults suffer from very low prosecution and conviction rates especially in the absence of DNA evidence. As a result, the forensic community needs to utilize other forms of trace contact evidence, like lubricant evidence, in order to provide a link between the victim and the assailant. METHODS: In this study, 90 personal bottled and condom lubricants from the three main marketing types, silicone-based, water-based and condoms, were characterized by direct analysis in real time time of flight mass spectrometry (DART-TOFMS). The instrumental data was analyzed by multivariate statistics including hierarchal cluster analysis, principal component analysis, and linear discriminant analysis. RESULTS: By interpreting the mass spectral data with multivariate statistics, 12 discrete groupings were identified, indicating inherent chemical diversity not only between but within the three main marketing groups. A number of unique chemical markers, both major and minor, were identified, other than the three main chemical components (i.e. PEG, PDMS and nonoxynol-9) currently used for lubricant classification. The data was validated by a stratified 20% withheld cross-validation which demonstrated that there was minimal overlap between the groupings. CONCLUSIONS: Based on the groupings identified and unique features of each group, a highly discriminating statistical model was then developed that aims to provide the foundation for the development of a forensic lubricant database that may eventually be applied to casework. Copyright © 2017 John Wiley & Sons, Ltd.

Characterizing and classifying water-based lubricants using direct analysis in real time(®)-time of flight mass spectrometry.

Lubricant analysis is a relatively recent addition to the examination protocol in sexual assault cases by the forensic science community. Currently, lubricants cannot be unequivocally identified, although their presence can be determined based on the detection of a few chemical components, i.e. polydimethylsiloxane, polyethylene glycol, glycerol or nonoxynol-9. Confirmation of their presence typically requires that an authentic reference sample be submitted and compared to the unknown sample to determine if they potentially came from the same source. In this study, 33 individual personal water-based lubricants were characterized by direct analysis in real time-time of flight mass spectroscopy (DART-TOFMS). The resultant mass spectral data were evaluated using well-established multivariate statistical techniques, such as principal component and linear discriminant analysis. Statistical analysis revealed six different groupings within the data that could be correlated to sub-categories of water-based lubricants that contain additives in the form of anesthetics, sensation enhancers and flavorings. This variability in the personal lubricant sources can be utilized to aid in identifying the specific type of lubricant when only a questioned sample is available.

Quantifying the degradation of TNT and RDX in a saline environment with and without UV-exposure.

Terrorist attacks in a maritime setting, such as the bombing of the USS Cole in 2000, or the detection of underwater mines, require the development of proper protocols to collect and analyse explosive material from a marine environment. In addition to proper analysis of the explosive material, protocols must also consider the exposure of the material to potentially deleterious elements, such as UV light and salinity, time spent in the environment, and time between storage and analysis. To understand how traditional explosives would be affected by such conditions, saline solutions of explosives were exposed to natural and artificial sunlight. Degradation of the explosives over time was then quantified using negative chemical ionization gas chromatography mass spectrometry (GC/NCI-MS). Two explosives, trinitrotoluene (TNT) and cyclotrimethylenetrinitramine (RDX), were exposed to different aqueous environments and light exposures with salinities ranging from freshwater to twice the salinity of ocean water. Solutions were then aged for up to 6 months to simulate different conditions the explosives may be recovered from. Salinity was found to have a negligible impact on the degradation of both RDX and TNT. RDX was stable in solutions of all salinities while TNT solutions degraded regardless of salinity. Solutions of varying salinities were also exposed to UV light, where accelerated degradation was seen for both explosives. Potential degradation products of TNT were identified using electrospray ionization mass spectrometry (ESI-MS), and correspond to proposed degradation products discussed in previously published works [1].

Screening for trace explosives by AccuTOF™-DART®: an in-depth validation study.

Ambient ionization mass spectrometry is finding increasing utility as a rapid analysis technique in a number of fields. In forensic science specifically, analysis of many types of samples, including drugs, explosives, inks, bank dye, and lotions, has been shown to be possible using these techniques [1]. This paper focuses on one type of ambient ionization mass spectrometry, Direct Analysis in Real Time Mass Spectrometry (DART-MS or DART), and its viability as a screening tool for trace explosives analysis. In order to assess viability, a validation study was completed which focused on the analysis of trace amounts of nitro and peroxide based explosives. Topics which were studied, and are discussed, include method optimization, reproducibility, sensitivity, development of a search library, discrimination of mixtures, and blind sampling. Advantages and disadvantages of this technique over other similar screening techniques are also discussed.

Characterization of automobile float glass with laser-induced breakdown spectroscopy and laser ablation inductively coupled plasma mass spectrometry.

A comparative analysis of the discriminating power of laser-induced breakdown spectroscopy (LIBS) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), each coupled with refractive index (RI) measurements, is presented for a study of 23 samples of automobile float glass. Elemental emission intensity ratios (LIBS) and elemental concentration ratios (LA-ICP-MS) and their associated confidence intervals were calculated for each float glass sample. The ratios and confidence intervals were used to determine the discrimination power of each analytical method. It was possible to discriminate 83% of the glass samples with 99% confidence based on LIBS spectra alone, and 96-99% of the samples could be discriminated based on LIBS spectra taken in conjunction with RI data at the same confidence level. LA-ICP-MS data allowed for 100% discrimination of the samples without the need for RI data. The results provide evidence to support the use of LIBS combined with RI for forensic analysis of float glass in laboratories that do not have access to LA-ICP-MS.

Adsorption saturation and chromatographic distortion effects on passive headspace sampling with activated charcoal in fire debris analysis.

Distortion of the chromatographic profile obtained for hydrocarbons that have been sampled by adsorption onto activated charcoal is a well-known phenomenon. The work reported here helps to better define the causes of chromatographic profile distortion and offers a potential method to avoid chromatographic distortion in some cases through a subsampling technique. The recovery of hydrocarbons from an equimolar mixture was investigated to determine the influence of hydrocarbon concentration on the molar ratios of recovered components. In a one-quart container, hydrocarbon volumes as small as 24 microL (liquid) were sufficient to saturate the surface area available for adsorption on a 99.0 mm2 square of activated charcoal, resulting in significant distortions in the molar ratio and the chromatographic profile of the recovered hydrocarbons. Passive headspace sampling of a similarly small volume of unweathered gasoline spiked onto carpet padding resulted in a significant distortion of the chromatographic profile. The chromatographic profile of the recovered hydrocarbons closely resembled 75% weathered gasoline. Heating the container spiked with unweathered gasoline to evenly distribute the components and then removing a subsample of the carpet padding to a second container for passive headspace analysis greatly reduced the amount of distortion in the resulting chromatogram.