Qualitative Analyses of Textile Damage (Cuts and Tears) Applied to Fabrics Exposed to the Decomposition of Carcasses and Associated Insect Activity in an Austral Summer.

Fatal stabbings are the leading cause of homicide in countries with restricted access to firearms, such as Australia. The analysis of damage on clothing imparted by a sharp object can assist in the characterization of the weapon. However, decomposition and carrion insects can modify the features of the damage, impeding textile damage analysis and crime reconstruction. This study aimed to identify and characterize the modifications of textile damage over 47 days of decomposition during the summer season in Western Australia. Fabric modifications were analyzed on cotton, synthetic, and blended fabrics with standardized cuts and tears, wrapped on 99 stillborn piglets. Six unclothed piglets acted as controls, with three being stabbed. All piglets were placed simultaneously in the field alongside swatches of fabric. Analyses considered taphonomy, insect interactions, and any textile damage using optical microscopy and SEM. The results showed that carrion insects can modify existing cuts and tears and introduce new artifacts on textiles. The 100% cotton fabric was the most affected by mechanical and chemical degradation, especially cuts and areas stained with blood or decomposition fluids. The study highlights the combined effect of multiple factors on textile damage, including the type of fabric, initial damage, bloating, insect activity, and biodegradation.

Condom evidence: Characterisation, discrimination and classification of pyrolysis-GC-MS profiles.

Analysis of condom evidence commonly focusses on the detection of silicone-based lubricants, such as polydimethylsiloxane (PDMS). Although various instruments are used to analyse silicone lubricants, pyrolysis-gas chromatography coupled to mass spectrometry (py-GC-MS) is one of the few instruments that presents immediate applicability to casework. However, considering that this technique detects silicone-based evidence, it is important to evaluate the discrimination potential of the method when applied to various samples. Examination of the variability within a large sample set from an international market is needed to evaluate the most distinguishing compounds likely to be detected in casework. In this study, 70 condoms, personal hygiene products, and lubricants, were analysed using py-GC-MS. Resulting pyrograms were characterised using published spectral databases. Pyrolysates data were extracted and evaluated using multivariate techniques. Qualitative visual inspection of the data, as well as statistical analysis, revealed at least five groups within the dataset. Discrimination was based on four main oligomers, as well as six minor compounds from siloxane degradation. Condom lubricants were found to present a very regular pattern, allowing for the majority of them to be differentiated from personal lubricants.

A forensic international market survey of condom lubricants and personal hygiene products using ATR-FTIR coupled to chemometrics.

Condom residues may be encountered in forensic investigations as traces in sexual assault or rape cases. Casework studies have shown the value of distinguishing condom residues from other types of personal products used by women. However, up to now, there has been no investigation of their chemical variability within an international context. This work employed attenuated total reflectance Fourier transform infrared spectroscopy with chemometrics to provide objective characterisation of condom lubricants and personal hygiene products from the international market. 166 samples were obtained covering five major classes of products likely to be used by women. Principal component analysis distinguished most major classes based on their spectral profiles, with subsequent support vector machine models yielding discrimination accuracies over 90%. A two-step approach was subsequently developed and enabled both classification and a discrimination accuracy of 100%. This could provide greater confidence in chemical discrimination of residues from these products when conducting investigations and help assess the origin of the chemical profile obtained. Further testing using three validation sets produced an identification accuracy of 100% for generic classes, which may allow investigative leads to be more readily obtained from recovered evidence.

Characterization and classification of water-based compounds in condoms and personal hygiene products using GC-MS.

Analysis of condom evidence commonly focusses on the detection of silicone-based lubricants, such as polydimethylsiloxane. However, water-based compounds such as propylene glycol or glycerin can also be used as condom lubricants and may, therefore, be detected as transferred traces. Evaluation of the variability amongst a large sample set from an international market is needed to determine what are the most likely compounds that may be detected in casework. In this study, 165 condoms, personal hygiene products, lubricants, creams and oils were analysed using gas-chromatography coupled to a mass spectrometer detector (GCMS). The resulting compounds were identified using mass spectral databases, then the data were extracted and evaluated using established multivariate statistical techniques, such as principal component analysis and discriminant analysis. Qualitative visual inspection, as well as statistical analysis, revealed at least twelve different groupings within the dataset. Discrimination was based on variations in the concentration of major compounds, as well as the presence or absence of minor compounds, such as anaesthetics. For the 127 condoms examined, 2 were exclusively water-based lubricated (1.5 %) and 6 contained silicone and water-based components (4.7 %). All the others were only silicone-based (119 condoms, 93.7 %). Strong variation was observed between the different sources of products. Personal hygiene products (PHP), creams, lubricating oils, personal lubricants, and condoms were found to have different chemical compositions. Hence GCMS can be used to assist in the differentiation of water-based residues for investigative purposes.

The effect of environmental degradation on the characterisation of automotive clear coats by infrared spectroscopy.

This paper presents a study into the chemical changes occurring within automotive clear coats as a result of environmental weathering, and their potential effect upon the characterisation of samples using infrared spectroscopy combined with chemometric modelling. Testing of three samples, collected from separate vehicles, exposed to the outside environment revealed no changes in model predictions over a 175 day period; however, incorrect predictions were observed following 435 days of exposure. Inspection of the corresponding infrared spectra revealed that these changes were likely due to the hydrolysis and photodegradation of polymer chains present in the clear coat, which were not observed in samples stored away from the outside environment over a one-year period. Analysis of previously weathered samples using synchrotron infrared microscopy found these changes occurred in a top-down fashion rather than within the bulk of the clear coat. This indicates that although weathering may affect the surface characterisation of clear coats over time, the targeting of deeper portions of the clear coat layer may still provide useful information as to the identity of the vehicle.

Synchrotron FTIR characterisation of automotive primer surfacer paint coatings for forensic purposes.

Synchrotron FTIR microspectroscopy was used to characterise and assess the chemical diversity of electrocoat primer, primer surfacer and basecoats of automotive paint samples from 75 vehicles representing a range of international car manufacturers. Significant diversity was found in the synchrotron FTIR data from the primer surfacer coats. Classification using principal component analysis revealed 14 discrete groups, which could be associated with the country of manufacture, the specific manufacturer and manufacturing plant, the year of manufacture of the vehicle and in some instances the number of layers in the paint system. The model generated from the primer surfacer was significantly more discriminating than a previous model generated from FTIR analysis of clear coats of the same vehicles. Analysis of the primer surfacer also avoids issues of possible environmental degradation and component migration seen with FTIR analysis of automotive clear coats. Providing such information concerning vehicle origin would aid in the development of investigative leads from the analysis of questioned automotive paint samples located at the scene of a crime or on the body/clothing of a hit and run victim.

Characterisation of chemical component migration in automotive paint by synchrotron infrared imaging.

Synchrotron infrared chemical imaging was employed to examine and assess the extent of interlayer component migration within multilayer automotive paint samples, with a particular emphasis on the cross-linking additive melamine. Two dimensional infrared chemical images revealed that melamine consistently diffuses in select paint samples from the underlying basecoat into the outermost clear coat layer. Pigments from the basecoat were also found to migrate into the adjoining layers. This is significant as the relative abundance of both melamine and pigments will vary greatly depending upon the region of the layer analysed. This component migration will undoubtedly impact the information gleaned from a questioned sample via library searching software or multivariate statistics. As a result, appropriate analytical protocols will need to be utilised to mitigate the effects of interlayer pigment and melamine diffusion, so as to afford a true representation of the composition of the coating for forensic identification purposes.