The evidential value of singed hairs in arson cases

The prevalence of singed hairs on hands was examined in a representative sample comprised primarily of Hamburg LKA staff members to determine the evidential value of such traces in criminal cases. Hair samples were taken from the hands of 160 subjects and examined under a microscope. Evidence of singing was found in 53 of the samples. These traces were largely restricted to a limited number of areas. Distribution of singed hairs over a wide area was observed in just 3 subjects all of whom reported contact with an open flame. The presence of singed hair on the back of the hand can be of great evidential value, though the corresponding distribution pattern must be carefully interpreted.     

The evidential value of black cotton fibres

Forensic scientists are faced with the problem of estimating the frequency of cotton fibres recovered in casework, in relation to those in the general population. One way of doing this is to consider the degree of spectral variation that occurs within a "block of colour". When a spectral pattern occurs very frequently, the evidential value of the fibres may be so low, that it is not worth considering them as target fibres. Using UV-visible range microspectro-photometry (MSP) spectra were recorded from 88 known black cotton dyes and 225 samples of black cotton taken from various textiles. UV-visible spectra originating from sulphur dyes and from the great majority of reactive and direct dyes can be easily recognised. Vat dyes present a little more difficulty. The degree of spectral variation and consequent discriminating power of MSP varied according to the dye class, from 0.13 for sulphur dyes to 0.93 for reactive dyes. From 99 textiles dyed with reactive dyes, the spectra could be divided into at least 40 varieties showing that these fibres have a high degree of individuality. Within the few direct dyes (11.5%) that were encountered, one basic spectral form predominated, but a number of minor variations were observed. Spectral information below 400 nm (UV-range) is important for making distinctions and is critical in the case of direct dyes.     

Evaluation and quantification of nuclear DNA from human telogen hairs

Nuclear DNA was extracted from human telogen hairs from 60 individuals. Six to nine hairs from each individual were individually extracted. The amount of DNA recovered from each individual varied greatly, and most samples yielded a quantity of 550 pg or less per hair. A selective extraction buffer was used to remove epithelial cell DNA and the amount of exogenous DNA was determined. DNA was also quantified by real time PCR using three different sized amplicons targeting an Alu sequence. The results were used to determine the state of degradation of the extracted DNA. Different quantities of sample (<100 pg, 100-500 pg, >500 pg) were amplified with the Miniplex kits to determine the minimum DNA template required for successful amplification. DNA recovered from hair showed degradation; however, partial profiles were obtained for those samples containing at least 60 pg using MiniSTRs.     

Adhesive tape analysis: establishing the evidential value of specific techniques

This study investigated the evidential value of specific methods of analysis for packaging tapes and clear adhesive tapes available in Australia. Fifty-eight adhesive tapes were analyzed using a wide range of optical, physical, and chemical techniques. The results were collated for the purpose of creating an Australian database of adhesive tapes, which would be of assistance in criminal investigation. Each technique was evaluated for its discriminating power, both for comparative purposes and for the identification of adhesive tapes by comparing unknown samples with the database. The combined discriminating power of the techniques applied is very high. It is possible to individually identify the source of an unknown adhesive tape sample in many instances by searching the database. It is also possible to form an opinion on the significance of a failure-to-discriminate result in comparative casework. Further work is still needed to expand and update the database, as well as compiling data on the relative market share of various products.     

Sex determination from plucked human hairs without epithelial root sheath

For sex determination, it is difficult to examine the sex chromatin in the hair root devoid of the epithelial root sheath because of melanin deposition in the hair cortex cells. In the present study, the possibility of determining sex was sought by observing the frequency of Y chromatin in the nuclei of hair cortex cells from human hair root devoid of epithelial root sheath. The male hair contained nuclei in each of which one brightly fluorescent spot was recognizable. The average frequency of the fluorescent spot in the hair cortex nuclei observed in 90 samples from 30 males was 59.4%; the maximum frequency was 74% and the minimum 37%. On the other hand, the fluorescent spots were rarely found in the nuclei of hair cortex cells from female hair. The frequency of occurrence was 5.3% on average, the maximum frequency being 12%, the minimum 0%. The frequency distribution of the male group and female group exhibited two discontinuous peaks. The frequency of the fluorescent spots can therefore be used as a criterion for determining sex. The fluorescent spot in dried male hair was shown to be detectable in a frequency of 20 – 40% 4 weeks after plucking, indicating that the nuclei of hair cortex cells can be subjected to the examination for at least this period if the hair has been kept in a dry condition.     

A study to investigate the evidential value of blue gel pen inks

The aim of this project was to investigate the evidential value of blue gel pen inks in Europe. For this purpose, 33 blue gel pen inks, of different brands and models, representative of those available on the European market at the time of the study, were analyzed using three techniques: filtered light examination (FLE), Raman Spectroscopy (RS), and scanning electron microscopy (SEM). First, after visual examination (naked eye and stereo microscope), it was possible to classify the 33 inks into three groups described as: milky, metallic, and normal. This paper describes in detail the results obtained for the normal gel pen group. The ability of the techniques to discriminate gel inks between and within brands varied. The results indicated that RS and SEM were more discriminating than FLE. The greatest degree of differentiation was achieved when using a combination of RS and SEM techniques (discriminating power = 0.91). This study also highlights some problems concerning the identification of the brand of a gel pen from a written text.     

The evidential value of cosmetic foundation smears in forensic casework

Cosmetic foundation products are easily transferred to clothing and other surfaces as a result of contact with such objects. Examination of past cases involving cosmetics in New Zealand has shown cosmetic foundation to be one of the more common cosmetic products encountered. The aim of this research was to determine the most discriminating method for the comparison of transferred foundation with samples obtained from a known source in forensic casework. Fifty-three foundation samples were analyzed by Fourier transform infrared spectroscopy (FTIR), gas chromatography with a flame ionization detector (GC-FID) and scanning electron microscopy-energy dispersive X-Ray analysis (SEM-EDX). It was found that a 5 mm2 section of a light smearing was enough to provide detectable results. The discriminating powers for FTIR, SEM-EDX and GC-FID were 98.3, 93.8, and 82.0% respectively. A combination of all three techniques provided a discriminating power of 99.7%, meaning that almost complete discrimination was achieved between the foundation samples.     

Statistical comparison of dog and cat guard hairs using numerical morphology

Numerical features obtained from the guard hairs of dogs and cats (total 300 hairs per dog or cat) were statistically compared, in an attempt to discriminate between them. Using hairs from each of five mongrel dogs and cats, eight measurements (length (Len), maximum width (MaxWid), cross sectional maximum diameter, cross sectional minimum diameter, cuticular thickness of the cross section and three scale counts per 100 microm length (observed at three positions: distal third (disSC), middle (midSC) and the proximal third (proSC) portions) and five indexes (hair width index (HWI), medulla index (MI), hair index, cuticle index and the difference in scale counts between the distal and proximal parts (defSC)) were examined. The range for each numerical feature overlapped each other extensively, and none of the features permitted a discrimination between dog and cat hairs, based on the values obtained. However, 12 numerical features, except for the midSC, showed a statistically significant difference between dog and cat hairs, as evidenced by a t-test. For the purpose of comprehensively comparing numerical features and statistically discriminating between dog and cat hairs, a discriminant analysis between the two were carried out using a multiple regression analysis. Four types of discriminant functions produced by combining over five numerical features were examined. Dog and cat hairs could clearly be discriminated using any of the discriminant functions. Species discrimination using the discriminant function permitted the species of a dog or cat to be determined, based on the overall morphologies of various numerical features. When experimentally collected test samples were investigated using the discriminant function using Combination-2, consisting of eight numerical features (Len, MaxWid, MI, HWI, disSC, midSC, proSC and defSC), all 10 cat hairs were correctly determined to be cat hair and 22 of 23 dog hairs were correctly identified. This discriminant function produced good results for species discrimination between dog and cat hairs.     

The evidential value of peptidase A as a semen typing system

Human erythrocyte peptidase A (Pep A) displays a genetic polymorphism in blacks. Its occurrence in human semen was examined for its possible use as a semen typing system. Studies by starch gel electrophoresis, in which the Pep A was located by an improved method, were carried out on semen, semen stains, and vaginal swabs taken at known times after intercourse. In addition, a large number of vaginal swabs, negative for semen, were taken from females throughout their menstrual cycles and examined for Pep A activity. The results indicated that Pep A typing could be carried out on semen and semen stains. However, it was possible to determine the Pep A type on vaginal swabs only when they had been taken within about 3 h after intercourse.     

Fibres used in the construction of car seats — An assessment of evidential value

The evidential significance of car seat fibres has been investigated. Thirty six samples of car seat fabric were examined and the fibres catalogued according to their morphology and characteristics. The majority of car seat fibres were black or grey thick polyester fibres that were either dyed or pigmented. The MSP spectra produced were unlike those usually obtained from black or grey polyester fibres used in clothing. Tapings taken from car seats were examined for car seat fibres, various types were found showing that these fibres are expected to shed from the fabric albeit in low numbers, unless the vehicle is older. No fibres that matched the samples of the car seat fabric were found on the tapings of the car seats. One hundred garments were examined for car seat fibres, 10% of garments had populations of such fibres present and 41% had at least one car seat fibre present. None of these fibres matched the samples of the car seat fabric or those from the car seat tapings.     

Dealing with allelic dropout when reporting the evidential value in DNA relatedness analysis

A method is suggested that allows the use of loci that have shown allelic dropout in kinship analysis as used for disaster victim identification (DVI) and missing person work (MP). This approach uses an extension of a previously published approach to modelling allelic dropout. This method may salvage some information in cases where allelic dropout is hindering DVI or MP work particularly in reconciliations involving a large number of bodies and pedigrees. It should not replace the pursuit of more complete DNA profiles by the normal rework process for such samples.     

Dealing with allelic dropout when reporting the evidential value in DNA relatedness analysis

A method is suggested that allows the use of loci that have shown allelic dropout in kinship analysis as used for disaster victim identification (DVI) and missing person work (MP). This approach uses an extension of a previously published approach to modelling allelic dropout. This method may salvage some information in cases where allelic dropout is hindering DVI or MP work particularly in reconciliations involving a large number of bodies and pedigrees. It should not replace the pursuit of more complete DNA profiles by the normal rework process for such samples.     

Morphological characteristics of head hairs and hairs from other parts of the body in the population of Asia

The paper describes specific morphological features of hairs from the head, beard, chest, axilla, pubis of the native population of Syria, India, Lebanon, Jordan, Yemen, Nepal, Palestine, Bahrain, Iraq and some residents of the Eastern Europe (Russians, Belorussians, Ukrainians). The hairs were studied macroscopically and microscopically (light microscopy). Digital data on hair thickness and number of lines of cuticula pattern were analysed using methods of variance statistics. Original information on some macro- and microscopic characteristics of hair has been obtained for citizens of the above countries.     

Blocks of colour IV: the evidential value of blue and red cotton fibres.

Samples of blue and red cotton fibres were examined using light and fluorescence microscopy as well as UV/VIS microspectrophotometry and fluorescence microspectroscopy. The degree of fluorescence and spectral variation was recorded. Particular attention was paid to the recurrence of certain spectral patterns. The importance of spectral information in the UV range is emphasized again. Colour plays a critical role in the comparison of cotton fibres in forensic sciences. Normally, fibres producing spectral patterns that are frequently seen will tend to have a lower evidential value in criminal cases as the choice of putative sources is theoretically greater and vice versa. Besides black cotton, blue and red cotton fibres are very frequent in fibre casework. The very high discriminating power using a combination of light microscopy, fluorescence microscopy and UV/VIS microspectrophotometry shows that even blue and red cotton fibres can provide excellent evidence when involved in fibre transfer cases.