The use of microspectrophotometry for the identification of pigments in small paint samples

The visible reflectance spectra of a number of common pigments are presented. These were measured between 380 nm and 900 nm in paint films using the Nanospec 10S Microspectrophotometer. This data can be used in combination with a computer program based upon simple Kubelka-Munk theory to identify the pigments in paint samples. The use of this approach in forensic science is illustrated by examples from recent cases.     

Analysis and discrimination of architectural paint samples via a population study

This study involved the comparative analysis and discrimination of 964 architectural paint samples collected in the United States and Canada. The samples were evaluated to determine the extent to which randomly collected architectural finishes can be discriminated following standard operating protocols for paint analysis. The study also provides a basis for assessing the significance of a result in which a pair or group are undifferentiated. The techniques utilized were stereomicroscopy, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) with both backscatter electron imaging (BSI) and energy dispersive spectroscopy (EDS), and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). To assess the layer characteristics (e.g., number, color, sequence, thickness), stereomicroscopy was used with FTIR and/or SEM as needed. The use of visual and microscopic evaluations in concert with FTIR resulted in 42 undifferentiated pairs, a discrimination of 99.99%. Adding SEM and Py-GC/MS analysis resulted in further discrimination of 31 pairs, resulting in eleven undiscriminated pairs of samples. At the conclusion of the study, samples that remained undifferentiated proved to originate from the same source. Therefore, no random pairs were indistinguishable at the conclusion of all examinations.     

The discrimination of small fragments of household gloss paint by microspectrophotometry

A microspectrophotometer has been used to discriminate between sets of household gloss paints of the same British Standard colours obtained from different manufacturers. Reflectance spectra were obtained, over the range 390 to 900 nm, from paint top surfaces and individual cross-sectional layers. Comparison of the reflectance spectra enabled visually similar paints to be discriminated.     

Preparing samples for the recording of infrared spectra from synthetic fibers.

An improved technique for recording infrared spectra from minute amounts of synthetic fibers by using KBr micropellets is described. The procedure is the same for all commonly encountered synthetic fiber varieties; hence, no preliminary identification is required.     

Mini-STRs: A powerful tool to identify genetic profiles in samples with small amounts of DNA

Degraded human remains and crime scene evidences with small amounts of DNA typically reveal incomplete or null genetic profiles when using standard (large) STR amplicons. The technology of mini-STRs, using reduced-size STR amplicons, can help to recover information from these samples. In our Forensic Genetic Service several genetic profiles were obtained or completed using MiniFiler kit (Applied Biosystems) increasing the success rate in sample typing. In all studied cases no inconsistencies were found between profiles obtained with MiniFiler and Identifiler, suggesting that this mini-STR kit can be used to include low copy number (LCN) evidence profiles in STR databases.     

Simultaneous screening and detection of drugs in small blood samples and bloodstains

A gas chromatography-mass spectrometry (GC-MS) method is described for the screening and detection of morphine, codeine, cocaine, benzoylecgonine, methylecgonine, cocaethylene, delta-9-tetrahydrocannabinol (THC), 11-nor-9-carboxy-THC (THC-COOH), 11-hydroxy-THC (11-OH-THC), amphetamine, methamphetamine, 3,4-methylenedioxyamphetamine (MDA), 3,4-methylenedioxymetamphetamine (MDMA) and N-methyl-1-(3,4-methylenedioxyphenyl)-2-butanamine (MBDB) in small blood samples and bloodstains using solid phase SPE columns and a pipetting robot (Gilson Aspec XL). The detection limits are in the order of 1.62-4.10 ng/50 microl spot (amphetamines), 0.15-0.82 ng/50 microl spot (cannabinoids), 1.67-4.70 ng/50 microl spot (cocaine and derivatives) and 4.53-4.91 ng/50 microl spot (opiates) and the correlation factors are between 0.9957 and 0.9999. The method has proven useful in forensic cases with only small sample volumes or bloodstains.     

Forensic applications of infrared chemical imaging: multi-layered paint chips

This paper examines the potential of infrared chemical (hyperspectral) imaging as a technique for the forensic analysis of automotive paint chips in particular, and multicomponent (e.g., layered) samples in general. Improved sample preparation procedures for the infrared analysis of paint chips are detailed, with the recommendation that where mounting resins are chemically incompatible with the sample, it is better to mount and section the sample in a soft wax from which the sections can be removed and pressed into a KBr disk for transmission analysis. Infrared chemical images of multilayered paint chips have been successfully obtained, with the chief advantage over conventional infrared analysis being that thousands of infrared spectra are collected in a few minutes across the whole sample, at a spatial resolution of around 5 microm. As with conventional infrared spectroscopy, chemical species can be identified from their spectra, but the wealth of information available can be also extracted in a number of different ways that make multicomponent spectral (and hence chemical) comparisons between two samples easy to visualize and understand. In one approach, the infrared chemical images of two paint chips being compared side-by-side can be viewed as a "movie," in which each frame is an intensity map of the two samples at a given wavenumber (frequency) value. In another approach, the spectra (pixels) in the image files are classified into chemically similar groups, resulting in a "cluster" image that makes it possible to simultaneously compare all of the layers in two paint chips. These methods are applicable to other multicomponent samples, and also to other chemical imaging techniques.     

百年中国立法的革命背景:一个重述与反思

中国近百年来的立法实践多与革命相伴,具有同质化的特点,带有明显的实用理性色彩,并且富有鲜明的政治诉求。中国百年的立法就是在革命式变法和变法式革命的往复中前行。基于当前对立法民主化和科学化的政治认同,中国革命式立法迎来了即将走出革命背景的历史机遇。     

Identification of tiny and thin smears of automotive paint following a traffic accident

Three complementary methods in the order of stereomicroscopy, micro-FT-IR spectroscopy and solubility tests were used for the purpose of matching known and questioned paint samples in an auto accident case. Grayish green paint smears scattered on a silvery gray coated plastic bar were taken from a blue car and referred to as questioned samples. Green paint chips were collected as known samples from a green car. These were analyzed to determine whether the paint smears found in the blue car could have been the transfers from the green car. Although each of the three methods, when used alone, suffered from unequal bases for making comparison (i.e., layering whole paint vs. smeared paint), insufficient specificity of methodology and the interfering background coating beneath the smeared paint, the limitations were significantly relieved when three methods were used in combination. Based on the results presented in this report, the questioned grayish green paint smears collected from the blue car and the known green paint chips from the green car are of the same class of paint; that is, the possibility of the above stated paint transfers cannot be eliminated.     

Biomedical patents and ethics: a Canadian solution

World Trade Organization member states are preparing for the upcoming renegotiation of the Agreement on Trade-Related Aspects of Intellectual Property Rights. One of the important elements of that renegotiation is the ethical considerations regarding the patenting of higher life forms and their component parts (e.g. DNA and cell-lines). The interface between the genetic revolution, patentability, and ethical considerations is the subject of this article. The author identifies, explores, and critiques four possible positions Canada may adopt in respect of patentability of biomedical material. First, Canada could do nothing. This approach would mean keeping biomedical materials outside the patent system and outside the stream of commerce. Canada would simply wait for an international consensus to develop before adopting a position of its own. Second, Canada could go it alone. It could implement a policy that balances the incentive effects of patents with the need to incorporate ethical and social values into the decision-making process regarding the use of biomedical materials. In respect of this option, the author proposes a model whereby non-profit bodies would hold the exclusive rights to research, use, and exploit biomedical materials. Third, Canada could follow the United States, Europe, and Japan by providing for almost unrestricted patenting of biomedical materials. This would be the most industry-friendly alternative. The fourth and final option is to use the medicare system to promote discussion of ethical considerations involved in the use of biomedical materials. The power of provincial health agencies may be used as a lever to ensure the discussion of ethical considerations concerning the use of biomedical materials. The author concludes that the fourth and final option is the best alternative for Canada while waiting for an international consensus to emerge.     

GC-MS analysis of hashish samples: a case of adulteration with colophony

This report describes the analytical characterization of 16 hashish samples confiscated in Italy. The samples were solvent extracted and subjected to GC-MS analysis for the separation and quantitation of the main cannabinoids. One of the analyzed samples was shown to contain extraneous compounds, identified as resin acids characteristic of colophony (rosin). Colophony is a natural resinous product obtained from various species of pine, spruce, and larch; it is a skin sensitizer and its fumes produce nonspecific irritation that can cause bronchial asthma. Similar adulterations of hashish have not been reported previously; therefore, at present there is no information about the effects of smoking colophony or a combination of hashish and colophony. It is presumed, however, that such a combination would be highly detrimental to the health of the user.     

Thermal shrinkage of small single acrylic fibers — A technique of forensic potential

Single fibers less than 1 mm long of nine types of acrylic fibers were thermally shrunk from 85°C to 285°C by hot stage optical microscopy. A surprisingly wide variety of behavior was observed. The temperature for the onset of shrinkage ranged from 105°C to 190°C; total contraction ranged from 2% to 64%; and some fibers contracted rather steadily, whereas others contracted abruptly. Reproducibility of shrinkage was excellent for most monocomponent fibers but was less reproducible for bicomponent fibers. In general, it was found that the technique may be used to discriminate among fiber types within a single fiber generic class using submicrogram sized samples.