The population of coloured textile fibres in domestic washing machines.

A population survey was carried out to analyse examples of the coloured fibre population that may be expected to exist in both front- and top-loading domestic washing machines during Spring, in Sydney, Australia. White cotton T-shirts were washed both individually, and with a normal household wash load, then taped to recover extraneous fibres transferred during the wash cycle. Twelve thousand one hundred and seventy-eight fibres were classified according to length, colour and generic class. Cotton fibres were most prevalent (69.4%), followed by man-made fibres (24.2%). The most common colour/generic class combinations were black/grey cotton (27%), blue cotton (20%) and red cotton (15.6%). Other combinations generally represented under 2% of the total fibre population. Two thirds (65.9%) of the recovered fibres were under 2 mm in length, the proportion of fibres decreasing with increasing fibre length. Variations in machine type did not affect the distribution of fibres with respect to fibre type, colour or length.     

A textile fibre survey as an aid to the interpretation of fibre evidence in the Sydney region.

Frequency figures of the fibre population on textile cinema seats were measured in Sydney, Australia, in winter. Sixteen seats were analysed from a very popular cinema complex, with 3025 fibres classified according to colour, generic class and fluorescence properties (100 grey-black cotton fibres only). The recovered fibres were mostly natural fibres (84%) with cotton the most common generic type (70%). On the contrary, man made fibres were relatively rare (15%) with rayon constituting the majority of these (51%). The most common colour/generic class combinations were grey-black cotton (33%) and blue cotton (30%) accounting for 63% of the total population. All other frequencies were below 5%, most below 1% using only the two properties of colour and generic class. Fluorescence properties were found to be very discriminating as far as grey-black cotton fibres were concerned. These features are considered and discussed and in particular, to emphasise the significance of fibres as evidence of contact.     

The individuality of fibres used to provide forensic evidence--not all blue polyesters are the same.

Fibres used in forensic casework suffer from a disadvantage common to other forms of trace evidence--it is not possible to state with absolute certainty that they originate from a specific source. Target fibre studies, population studies and research on 'blocks of colour' have effectively demonstrated the polymorphism of textile fibres (particularly man-made ones) and have shown that when a fibre is believed to have a specific putative source, the chance that it has originated from a different source purely by coincidence is extremely remote. A study by Houck MM (Houck MM, Inter-comparison of unrelated fibre evidence. Forensic Science International 2003; 135: 146-149) has shown that no coincidental matching fibres were recovered from items of clothing examined in 20 unrelated crimes. The study involved over two million comparisons. This work goes a step further, and using the example of blue polyester fibres shows that even within a very narrow segment of the whole general fibre population, many examples of a specific colour/type of man-made fibre taken from random sources can be compared and the chance of any two being the same is very low. These studies should help to show the specificity and value of transferred fibres in providing forensic evidence.     

The kinetics of colour change in textiles and fibres treated with detergent solutions: Part II — Spectrophotometric measurements

The aim of this study was to assess colour variations that occur in several types of textiles and their constituent fibres, resulting from the long-term influence of various laundry detergents. A 14-day experiment was conducted using blue, red and grey/black cotton, wool, acrylic and polyester textiles. The spectrophotometric measurement of colour changes in fabric samples and test solutions, as well as the microspectrophotometric analysis of colour changes in single fibres were described. An evaluation of the observed colour changes from a forensic fibre analysis expert's point of view, as well as that of an average user/consumer of the textiles and laundry detergents is also provided.     

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.     

The kinetics of colour change in textiles and fibres treated with detergent solutions: Part I—Colour perception and fluorescence microscopy analysis

The aim of this study was to assess colour changes that occur in several types of commonly available textiles as a result of the long-term effects of various popularly used laundry detergents. A 14 day experiment was conducted using blue, red and grey/black cotton, wool, acrylic and polyester textiles. Colour changes were evaluated through the visual comparison of the colour of the textile samples against that of the untreated (control) material.The kinetics of the changes in the colour of the fibres were monitored using fluorescence microscopy (UV excitation filter). The conclusions include an assessment of the observed changes from a fibre analysis expert's point of view, as well as that of an average user/consumer of the products involved.     

Raman spectroscopy and the forensic analysis of black/grey and blue cotton fibres Part 1: investigation of the effects of varying laser wavelength

Raman spectroscopy was investigated to determine the optimal conditions, mainly laser wavelength/s, for the analysis of the commonly encountered black/grey and blue cotton fibres dyed with reactive dyes. In this first part, a single blue cotton fibre, its three dye components, and an undyed cotton fibre were analysed with five different laser wavelengths from two different Raman microprobe spectrometers. The quality of the spectra, fibre degradation and speed of acquisition were used to determine that, under the conditions used, the 785 and 830 nm lasers gave superior results. The 632.8 nm laser wavelengths provided good results with little acquisition time and no spectral degradation. Results indicate that, at least, the major dye component could be identified using Raman spectroscopy.     

The population,transfer and persistence of fibres on the skin of living subjects

Fibres were transferred to the bare arms of living subjects and their persistence determined at intervals up to 24 h, during which normal daily activity was undertaken. Decay curves showed an initial rapid loss followed by an apparently exponential decay. No target fibres were found to remain after 24 h. The length distribution showed a shift towards shorter fibre lengths and the differential shedding results for a polyester/cotton mixture showed a small bias towards the retention of cotton. The population of coloured fibres on bare skin was classified according to perceived colour, length, generic class and the presence or absence of delustrant.     

A study in relation to the random distribution of four fibre types on clothing (incorporating a review of previous target fibre studies).

A new target fibre study was undertaken building upon eight previous published studies, which are reviewed here. Fifty-eight items of outer clothing, obtained from households across England, were taped and searched for three types of commonly occurring fibres and one less common fibre type. The tapes were examined using a combination of automatic and manual searching. Any fibres similar to the target fibres were removed and examined using microspectrophotometry, comparison microscopy, thin layer chromatography (TLC) and fourier transform infrared spectroscopy (FTIR) where applicable. One polyester fibre, four acrylic fibres and eleven wool fibres were found that matched the three commonly occurring target fibre samples. None of the less common polyester fibres were found. One item had six matching wool fibres and another had the polyester fibre and an acrylic fibre recovered from it. The remaining eight fibres were each recovered from individual items. The results suggest that finding a large number of fibres that match a control is unlikely to happen by chance, which supports the findings of the previous target fibre studies.     

运用光谱成像技术区分同色棉纤维

目的研究同色棉纤维的检验方法。方法运用成像光谱法对红、蓝、黑3个颜色组的棉纤维进行区分。结果红色棉纤维的鉴别率为62．2％，蓝色棉纤维的鉴别率为77．8％，黑色棉纤维的鉴别率为69．6％。结论实验结果表明，光谱成像技术可以区分大部分同色棉纤维。拓宽了纤维检验的方法，解决了同色棉纤维的区分问题，该方法能够用于对微量同色棉纤维的快速鉴别。     

The secondary transfer of fibres from head hair.

In this study, the effects of fibre type, hair style, time and fibre persistence on the secondary transfer of mask fibres to pillowcases via head hair were studied. Volunteers with a range of hair styles, and masks consisting of different fibre compositions were used in the study. Fibres from the masks were found to transfer from donor subjects to the pillowcases up to 14 nights after the mask had been worn. On average, the number of secondarily transferred fibres found decreased with time; however, this decrease appeared to be more 'linear' in nature, rather than an exponential decay. The greatest degree of secondary transfer occurred with cotton, then acrylic, then wool. In a primary transfer/persistence experiment with a 50% acrylic/50% wool mask, wool was found to persist in the hair more readily than acrylic. The results also showed that the greatest degree of secondary transfer occurred via short straight and long straight hair, with no clear pattern emerging between medium length hair (both straight and curly) and with long curly hair. The implications of these findings for the assessment and interpretation of casework are considered along with data obtained from related studies.     

A population study of polyurethane foam fragments recovered from the surface of 100 outer-garments

One hundred outer-garments were examined for microscopic fragments of polyurethane foam. Low power stereomicroscopy was used to classify fragments into 18 groups according to macroscopic colour. Amber, pale yellow and black were the most frequently encountered, whilst navy, pale blue, bright pink, beige, brown, pale green, peach and white were the least frequently encountered. High power comparison/fluorescence microscopy was used to discriminate 166 populations within 16 colour groupings. The majority (95.2%) of populations consisted of three fragments or less. This study demonstrates that the background population of foam fragments on an outer-garment consists of low numbers representing various colours. Therefore, finding a large population of microscopically indistinguishable fragments within a casework situation has the potential to be considered highly significant evidentially.     

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.     

The recovery of fibres from non-textile items using a static charge

This study investigated a new method of fibre recovery from non-textile items using polystyrene rods which have a static charge. A range of natural and man-made fibres were used on a number of substrates, including weapons, paper and plastic bags. The average recovery rate from all substrates was 99.1%. The effect of humidity on fibre recovery was also studied and it was found to reduce the ability of the rods to recover fibres. However this is unlikely to be an issue if recovery takes place in a forensic laboratory. It was concluded that the rods would prove a beneficial addition to the forensic laboratory as a relatively quick method of fibre recovery from non textile items where the standard method of recovery using tape lifts cannot be used.     

The analysis and comparison of blue wool fibre populations found at random on clothing.

Fifty-eight garments were taped and searched for mid to dark blue wool fibres. These were then removed from the tapings, mounted on slides and examined using a high-power microscope (400x). A total of 2,740 blue wool fibres were identified and visible range microspectrophotometry (MSP) was performed on them. Three hundred independent blue wool populations were identified on 56 of the 58 garments searched. The lack of control fibres meant the spectral range of each population was unknown. The number of populations may have been underestimated by grouping together the fibres that had broad single peaks and a lack of distinguishing features in the spectra. Although blue wool is considered to be a common fibre type, 300 unique spectral shapes were identified by the use of microspectrophotometry alone. This demonstrates that the dyes used in the dyeing of blue wool are variable. Showing that many different populations of blue wool occur on a range of garments should ensure that the forensic scientist does not underestimate or understate the strength of evidence in cases where blue wool is found. Hopefully this work will enlighten scientists and enable them to also assess the true value of their findings when other commonly occurring fibres are encountered.     

The discrimination of (non-denim) blue cotton

This study was conducted to determine the degree of discrimination obtained between non-denim blue cotton fibres using visible–UV range microspectrophotometry alone. To this end, samples of fibres were taken from 100, non-denim, blue cotton, outer garments, including t-shirts, trousers and jumpers and subjected to analysis by both visible and UV range microspectrophotometry. The results obtained from the samples of each garment were compared to determine if they ‘matched’ or not. From an initial visual comparison of the garments it was possible to subdivide the samples into two populations consisting of 73 ‘dark blue’ garments and 27 ‘mid-blue’ garments. It was found that of the 73 ‘dark blue’ garments, 22 distinct sub-populations could be distinguished using visible range MSP, this figure being increased to 43 when the analysis was extended into the UV range. In the case of the 27 ‘mid-blue’ garments, 9 distinct sub-populations were discriminated using visible range MSP, this figure being increased to 17 when the analysis was extended into the UV range. The discriminating power (i.e. the number of discriminated pairs divided by the number of possible pairs) of visible range microspectrophotometry was calculated as 0.89 for ‘mid-blue’ garments and 0.87 for ‘dark blue’ garments. Extending microspectrophotometry into the UV range increased discrimination by 7%, giving a discriminating power of 0.96 for both mid and dark blue cotton fibres which was similar to that reported by a previous study where this method was combined with light and fluorescence microscopy.Intra-garment variation was found to be negligible. The implications of this study for casework are discussed and a revised analytical pathway for the comparison of this fibre type/colour combination using microspectrophotometry as a primary screening tool, is proposed.     

The ageing of bruises: a review and study of the colour changes with time.

This work was inspired by a recent case of child abuse where the question of the age of the bruises on the body was raised. The first part of this paper reviews published work on bruises. It illustrates the paucity of work in this field and the absence of studies of the colour changes in bruises of human skin with time. The second part of this paper consists of our own study of the appearance of bruises. The aim was to identify the colour changes which occur in bruises and over what time-scale, in order to determine whether bruises can be aged by appearance. A total of 369 photographs were obtained of bruises aged less than 6 h and up to 21 days old, in 89 subjects aged 10-100 years. It was found that the development of a yellow colour was the most significant change (subjects aged less than 65, P less than 0.001; subjects aged greater than or equal to 65 years, P less than 0.001). The development of a yellow colour occurred significantly faster in subjects aged less than 65 years. (P less than 0.001). The appearance of a blue and purple/black colour was of lesser significance. The appearance of a red colour did not alter significantly with time. From this study it was only possible to conclude that a bruise with a yellow colour was more than 18 h old.     

The configuration of cervical spinous processes in black and white South African skeletal samples

The present study investigates the frequency of bifidity/nonbifidity in the black and white South African populations. Four-hundred skeletons of known race, sex, and tribal group were examined. Spinous processes were classified as bifid (bifurcate and cleft subtypes) and nonbifid (obtuse, pediculate, acinate, and clavate subtypes). Statistical analysis using the chi-squared probability test (p < 0.05) was carried out. Bifid spinous processes were present significantly more frequently in the white sample (58.9%) than in the black (31.6%). A bifid spinous process occurred most commonly in C2 (89%) followed by C5 (83%), C4 (79%), C3 (59.4%), and C6 (41.7%) in the white sample. A similar order of decrease in bifidity occurred in the black sample. C2 most commonly displayed the bifurcate subtype of spinous process, while the clavate subtype of nonbifid spinous process was the most common in both populations. The significantly higher frequency of bifidity in the white South African sample when compared to the black sample may suggest a population difference.     

Investigating the effect photodegradation has on natural fibres at a microscopic level

It is a known fact that when fabric is left exposed to sunlight photodegradation occurs. However, no study has ever looked at the photodegradation that occurs to individual fibre filaments as commonly recovered from a scene of crime. To look at photodegradation of individual fibres, wool and cotton fabric were dyed using CI Acid Red 27 and CI Direct Red 80 respectively at two depths of shade, 0.25% and 2.0% owf. Pieces of fabric and individual fibre samples were then placed in a Light Fastness Q-Sun 1000 Xenon test chamber which simulated exposure to sunlight over two time periods, 64 h (equivalent to one weeks sun exposure) and 128 hrs (equivalent to two weeks sun exposure). The resulting pieces of fabric and fibres where then examined using high power comparison microscopy, as well as graded for colour fading using SDC Grey Scale for Assessing Change in Colour (including half steps). Results show that in both fibre types, photodegradation occurs in all samples, however, the degree of fading is shown to vary within a given fibre population showing it is unpredictable in nature.     

Damage caused to fibres by vapour cloud explosions

Research on the very specific damage to single textile fibres caused by vapour cloud explosions is presented. Vapour cloud explosion experiments were carried out using a selection of 41 garments differing in colour, fibre composition and textile construction. Fibres subjected to a vapour cloud explosion become wider at the end, often taking the form of a ball, bulb or shovel, while the morphological structure of the remaining part of the fibre remains almost unchanged. The presented results can clearly indicate that an explosion took place at the scene of the crime. The authors would like to be able to provide investigators with specific information on how to link clothes (and thus people) to a specific type of crime.