Automotive flock and its significance in forensic fibre examinations

The interiors of fifty eight vehicles were examined and samples were taken. All vehicles had samples of flocked material in their interiors. Flocked material was found on the window channels, window frames, door edges and in glove compartments or central console compartments. The majority of flock fibres used in the vehicles examined were carbon black pigmented polyester or nylon. A variety of dyed nylon fibres were also used in the vehicles. The discrimination power of dyed flock fibres used in the interior of vehicles was found to be 0.974. The front seats of these vehicles were examined for loose flock fibres. All vehicles had flock fibres present on the front seats. In the majority of vehicles, flock originating from material in the vehicle's interior was present on the front seats of the vehicle. The number of flock fibres present on the front seats varied greatly from car to car but did not appear to be dependant on the type of seat fabric or on which areas in the car were flocked.     

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.     

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.     

Prevalence of organic gunshot residues in police vehicles

The present study investigated the organic gunshot residue (OGSR) background level of police vehicles in Switzerland. Specimens from 64 vehicles belonging to two regional police services were collected and analysed by LC-MS in positive mode. The driver’s and back seats were sampled separately to monitor potential differences between locations and to assess the risks of a suspect being contaminated by OGSR during transportation to a police station.The results showed that most of the 64 vehicles were uncontaminated (44 driver’s seats and 38 back seats respectively). Up to six of the seven targeted compounds were detected in a single sample, once on a driver’s seat and twice on back seats. The contamination frequency generally decreased as the number of compounds detected together increased. The amounts detected were in the low ng range and less than amounts generally detected just after discharge on a shooter. Our data indicated that detecting a combination of four or more compounds on a police vehicle seat appears to be a relatively rare occurrence. The background contamination observed was most probably due to secondary transfer from police officers (e.g. through recent participation in a shooting session or firearm manipulation) or from firearms stored in the vehicles. The present results might be used as a recommendation to minimize contact of a suspect with contaminated surfaces if OGSR is implemented in routine work in parallel to IGSR analysis.     

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.     

Secondary transfer of organic gunshot residues: Empirical data to assist the evaluation of three scenarios

The present study aimed at providing data to assess the secondary transfer of organic gunshot residues (OGSR). Three scenarios were evaluated in controlled conditions, namely displacing a firearm from point A to point B, a simple handshake and an arrest involving handcuffing on the ground. Specimens were collected from the firearm, the hands of the shooter and the non-shooter undergoing the secondary transfer in order to compare the amounts detected.Secondary transfer was observed for the three scenarios, but to a different extent. It was found that displacing a firearm resulted in secondary transfer in <50% of the experiments. The firearm also had an influence, as contrary to the pistol, no secondary OGSR were detected using the revolver. Shaking the hand of the shooter also transferred OGSR to the non-shooter's hand. In that case, the amount of OGSR was generally higher on the shooter than on the non-shooter. Finally, the largest secondary transfer was observed after the arrest with handcuffing with positive results in all cases using the pistol. In that scenario, the amounts on the shooter and the non-shooter were in the same range.This study highlights that the secondary transfer must be taken into account in the interpretation of OGSR. Indeed, an individual's hands might be contaminated by handling a firearm or having physical contact with a shooter.     

The transfer and persistence of automotive carpet fibres on shoe soles

The transfer and persistence of automotive carpet fibres to shoe soles was investigated. It was found that fibres were transferred with the normal activity of a car passenger. Carpet type and shoe sole parameters were significant determinants in the number of fibres that transferred. The average number of fibres was between about one and 33 per sole. Fibres that had been transferred after normal activity only persisted for a few minutes after walking. A survey of the shoe soles of people about to leave their car showed that fibres were usually present. The majority of shoe soles surveyed had less than five fibres with the greatest number of fibres found being 14. The likelihood of finding a large number of fibres on such soles is rare. Fibre composition of automotive carpets showed a high degree of variation. Grey was seen to be a common colour irrespective of the colour of the vehicle body.     

The propensity of individuals to deposit DNA and secondary transfer of low level DNA from individuals to inert surfaces

We have shown that there is a difference between individuals in their tendency to deposit DNA on an item when it is touched. While a good DNA shedder may leave behind a full DNA profile immediately after hand washing, poor DNA shedders may only do so when their hands have not been washed for a period of 6h. We have also demonstrated that transfer of DNA from one individual (A) to another (B) and subsequently to an object is possible under specific laboratory conditions using the AMPFISTR SGM Plus multiplex at both 28 and 34 PCR cycles. This is a form of secondary transfer. If a 30 min or 1h delay was introduced before contact of individual B with the object then at 34 cycles a mixture of profiles from both individuals was recovered. We have also determined that the quantity and quality of DNA profiles recovered is dependent upon the particular individuals involved in the transfer process. The findings reported here are preliminary and further investigations are underway in order to further add to understanding of the issues of DNA transfer and persistence.     

Electrically-induced collagen calcification in pig skin. A histopathologic and histochemical study

Deposition of calcium salts on collagen fibres in skin of fully anaesthetized pigs was induced by exposure to direct current (d.c.). In biopsies obtained from cathode areas successively from day 1 to day 7 after exposure the histopathologic and histochemical changes before and after the initial deposition of calcium salts have been examined. For comparison skin sites with intradermal injected calcium hydroxyapatite crystals were studied in addition. Small areas of calcified collagen and elastic fibres were noted in viable tissue 2 days after d.c. exposure. In succeeding days the calcified areas enlarged with new deposits always more superficial and closer to the epidermis than the original calcium deposits. Preconditions for calcification appear to be (1) a pH change in basic direction and/or the electrochemical processes specific to the cathode area and (2) a viable tissue. Elastic fibres appear to have a lower calcification threshold than collagen fibres. A positive staining for glycoproteins (PAS) and glycosaminoglycans (alcian blue pH 2.5) was noted in the calcified collagen fibres simultaneously with the calcification. In succeeding days the intensity of the staining reactions increased. Whether changes in the glycoproteins, collagen and its intimately bound glycosaminoglycans precede the calcification or the staining reactions develop secondarily to this deposition is not known. However, seven days after intradermal injections of Ca-apatite crystals in pig skin small and large crystals were observed ultrastructurally without any relation to collagen fibrils, but the calcified tissue presented a positive PAS and alcian blue reaction from day 2. Thus the PAS and alcian blue stainings in this model develop secondary to the deposition of calcium salts.     

Transfer of fibres on the hands of living subjects and their persistence during hand washing

Textile fibres were transferred to the hands of ten living subjects and their persistence was determined after hand washing. Average number of fibres transferred was 300 ± 133 (female 288 ± 92, male 311 ± 163) per 100 cm² hand area in the 100 experiments. However the number of fibres transferred was not gender dependent but individual dependent. The hand texture of subjects was compared with the number of fibres transferred but the relationship was not observed. The number of fibres transferred varied significantly for the 10 repeated experiments performed under the same conditions for the same subject.The subjects were then asked to wash their hands with water. One test group washed their hands with standing water, and the other with running tap water. Afterwards, the number of fibres remaining on the test subjects' hands were investigated. Migration of the fibres on the surface of the observed hands did occur but total loss of transferred fibre after hand washing did not occur. The average number of fibres remaining per 100 cm² hand area was 14 ± 10 (range = 3–72) for hand washing with standing water, and 10 ± 12 (range = 0–79) for washing with running tap water. The results of this study show the possibility of finding fibres on the hands of a person involved in a criminal case even after hand washing before fibre collection.     

Candidate gender and voting in the 1997 British general election: Did labour Quotas Matter?

The proportion of women MPs elected in the 1997 British general election reached an historic high of 18.2 per cent, the vast majority from the victorious Labour Party. The large increase in the proportion of women Labour MPs was partly due to the policy of establishing women‐only shortlists for winnable seats. This paper examines the distribution of women candidates in the election and analyses the factors that affected the votes they attracted. The results show that Labour women selected on the women‐only shortlists attracted significantly more votes than women nominated on open shortlists. This was mainly a consequence of their selection for marginal seats, but the greater organisational effort that was concentrated on those seats was also an important factor. Overall, there was no evidence that voters discriminated against women candidates in the election, regardless of party and regardless of how they were selected. The large number of women MPs raises issues concerning the formulation and articulation of a distinctive women's policy agenda at Westminster.     

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.     

On the frequency of occurrence of a peculiar polyester fibre type found in blue denim textiles

In a double murder investigation, the victims were found after a prolonged stay in a drainage canal. In spite of the expectations, fibre examination established a multitude of primary and secondary transferred fibres. One of these fibre types was a colourless polyester fibre possessing a blue coloured molten fibre end. These matched one of the types present in the suspect's blue denim trousers. The aim of this study was to verify the rarity of this peculiar fibre type and more precisely its presence in blue denim textiles. Over five hundred different blue jeans textiles were examined and only one of these presented exactly the same type. The comparison involved microscopy, microspectrophotometry in the visible range and Raman spectroscopy. The results indicate this fibre type is extremely rare in a blue jeans fabrics and that “standard” blue denim should not be disregarded in case work.     

An investigation on the secondary transfer of organic gunshot residues

Gunshot residues (GSR) are an important forensic trace in firearm-related events. Currently, routine GSR analyses focus on the detection and characterisation of the inorganic components (IGSR). The increasing prevalence of heavy metal-free ammunition challenges these current protocols and there is an increasing interest in how the organic components of GSR (OGSR) can provide complementary information. Similar to the situation with IGSR, OGSR compounds originally deposited on the shooter during the firing process may further be transferred onto another individual or surface. Hence, the aim of this study was to provide additional information regarding the risk of a secondary transfer of OGSR. Two scenarios were investigated, the first one related to the arrest process and the possibilities of a secondary transfer arising between a shooter onto a non-shooter (e.g. between a police officer and a person of interest (POI)). The second scenario concerned the transfer of OGSR onto the non-shooter after handling a firearm for few minutes without discharging it. One calibre was chosen, the .40 S&W calibre, used by several Australian State police forces. A secondary transfer was observed in all cases for the two scenarios investigated, for three compounds of interest: ethylcentralite (EC), diphenylamine (DPA), N-nitrosodiphenylamine (N-nDPA). The firearm handling scenario resulted in a larger secondary transfer to that of the arrest scenario. Overall, the amounts of OGSR detected on the non-shooter were generally lower than that detected on the shooter and controls after the arrest scenario. The results of this study provide complementary knowledge about OGSR, which can be further used to improve the current practice and the interpretation of OGSR evidence. In particular, it highlights that the secondary transfer proposition must be considered during the interpretation of forensic findings, especially when small amounts of OGSR target compounds are detected.     

The morphogenesis of electrically and heat-induced dermal changes in pig skin

In order to establish pathological evidence in dermis for distinguishing between sequelae of electrical torture and those of other superficial injuries, the skin of eleven fully anaesthetized Danish Landrace pigs have been exposed to heat and electrical energy from either 50 Hz alternating current (a.c.) or direct current (d.c.) via 12 mm large contact knobs or via a pointed 0.5 mm large electrode (only 50 Hz a.c.). The lesions have been examined from 1 to 126 days after the injury. While heat lesions exposed to energy lower than 60 joule only gave minor changes, heat lesions exposed to more than 60 joule showed changes in both collagen fibres (basophilic or eosinophilic fibres without any birefringence or coarse cross-striation in polarized light, respectively) and dermal cells (granular cytoplasm). Areas exposed to 50 Hz a.c. via 0.5 mm. electrode showed basophilic collagen fibres and in a few biopsies on day 7 calcium salts on collagen fibres. Using 12 mm large electrodes the changes were minor, but basophilic and eosinophilic collagen fibres with no birefringence or with fine/coarse cross-striation respectively were seen. Even cells with 'vesicular nuclei' were seen on day 1 and 2 after the injury. The changes in the anode area showed resemblance to that of heat lesions (basophilic collagen fibres). Eosinophilic collagen fibres with fine densely spaced cross-striation in polarized light and 'vesicular nuclei' as well as collagen fibres with calcium salts were seen in the cathode lesions. It is concluded that the dermal changes in the cathode area are specific for electrical injury from day 1 to 14. However, earlier studies have demonstrated dermal changes specific for electrical injury at day 0 and the presence of calcified collagen fibres up to 2 months after injury. The dermal changes in anode lesions were non specific and could not be differentiated from those found in heat lesions. Alternating current lesions (50 Hz) were specific from day 1 to day 7, when the pointed electrode was used, but only in a few days when the energy was transferred via the 12-mm electrodes.     

An innovative transfer DNA experimental design and qPCR assay: Protocol and pilot study

Forensic “touch” DNA samples are low-quantity samples that are recovered from surfaces that have been touched by single or multiple individuals. These samples can include DNA from primary contributors who directly touched the surface, as well as secondary contributors whose DNA was transferred to the surface through an intermediary. It is difficult to determine the type of transfer, or how often and under what conditions DNA transfer occurs. In this paper, we present an innovative protocol that combines (1) a paired male and female transfer DNA experimental design in which the presence of male DNA indicates secondary transfer and (2) a cost-effective quantitative PCR (qPCR) assay of a sex-specific region in the Amelogenin gene to detect male and female DNA. We evaluate the ability of the Amelogenin qPCR assay to detect low concentrations of male and female DNA in mixed samples. We also test experimental DNA samples using our transfer DNA protocol to differentiate primary and secondary DNA transfer. Male DNA was detected in the majority of known mixed samples, even in samples with 4× more female DNA—this result demonstrates the ability to detect low concentrations of male DNA and the presence of secondary transfer DNA in our experimental design. Primary DNA transfer was detected in 100% of our experimental trials and secondary DNA transfer was detected in 37.5% of trials. Our innovative protocol mimics realistic case scenarios to establish rates of primary and secondary DNA transfer in an inexpensive and simplified manner.     

A study of the potential risk of gunshot residue transfer from special units of the police to arrested suspects

The presence of gunshot residues (GSRs) on arrested suspects can help the Court to form an opinion regarding the possibility of utilization of firearms by these suspects. Since the presence of a few particles can in some cases already have a strong indicative value, the GSR experts have to evaluate in their daily work the risk of a potential contamination of these suspects during their arrest. A few studies conducted on police officers and police facilities concluded that the risk of secondary transfer on arrested suspects is quite negligible. However, the case of special force units of the police should be taken into account, since these units can be assumed to be highly contaminated by GSR due to their intensive training. The aim of this study is to evaluate this possibility of particle transfer by performing simulations of arrests by special force police units, according to both low and high contamination scenarios. The results show that secondary transfers of GSR during these simulations are in most cases not negligible, even for the low contamination scenario. This is especially apparent on the vests of the target persons, with an average of 7 GSR particles (2 PbBaSb and 5 TiZn) found on the stubs used on these materials. Of course, the major contamination levels were observed in the case of the high contamination scenario, due to the use of highly contaminated gloves by the police officers during the arrests. Some recommendations are proposed to take into account this risk of contamination and to try to minimize it, or at least to better identify it.     

Persistence of transferred fragrance on fabrics for forensic reconstruction applications

It has recently been established that volatile organic compounds (VOCs) successfully transfer between clothing even with a short contact of 10 s, highlighting the potential to use VOCs in forensic reconstruction scenarios, such as sexual assault cases. The mid and low volatility compounds transferred in greater amounts than high volatility compounds. This study presents empirical data addressing the persistence of transferred VOCs on clothing for the first time. A series of experiments were carried out to determine the persistence of VOCs on clothing for time periods of up 4 weeks, on natural and synthetic fibres, and at three different environmental temperatures. The data indicate that the highest VOC amounts are generally obtained for shorter persistence times of up to 1 d. Whilst high volatility compounds were not recovered in sufficient amounts to allow quantification, the four other transferred VOCs were successfully quantified for persistence times of up to 4 weeks. The persistence for mid-volatility compounds follows decay curve trends in line with those previously obtained for fibres, glass and pollen. When comparing the persistence of VOCs on a natural and a synthetic fibre, for a persistence time of 1 h, the transferred VOCs were retained on a natural fibre in higher amounts than on a synthetic fibre. However, for longer persistence times the concentration of VOCs was similar between the two fabrics. Lastly, lower environmental temperatures resulted in higher recoveries for most VOCs, especially for short persistence times. These findings demonstrate that optimal recovery of VOCs from clothing occurs when the fabric is kept at cooler temperatures and analysed soon after the fragrance transfer occurred, although VOC recovery was possible at higher temperatures and after longer persistence times. Given the transfer and persistence characteristics of VOCs from fragrance, there is potential for fragrance to be used as a form of trace in forensic reconstruction approaches.     

Addressing the alternate hypothesis: Transfer and persistence of saliva beneath fingernails

This study investigated the transfer and persistence of salivary DNA under fingernails. This was performed to address a common alternate hypothesis presented to scientists in court, asserting that a relatively large quantity of DNA detected beneath the fingernails, typically from a victim of crime, originates from innocuous transfer of saliva in a casual setting.It was determined through these studies that contact with liquid saliva was an effective way to transfer foreign DNA beneath fingernails. However, when saliva was dried, DNA did not readily transfer through casual contact.When liquid saliva was placed directly beneath fingernails the amount of DNA detected from the saliva donor twenty-four hours later was several hundred-fold lower than the amount detected when sampling occurred immediately following deposition. Furthermore, when the recipients’ hands were washed immediately following the deposition of liquid saliva beneath fingernails, the majority of foreign DNA was removed following one hand washing and all detectable foreign DNA was removed from most recipients’ hands after three or six hand washings.This study demonstrates that casual contact with wet saliva can result in the transfer of substantial quantities of DNA beneath fingernails but that it does not typically persist for extended periods of time and is mostly removed if the hands are washed soon after deposition.     

Is it possible to predict the origin of epithelial cells? – A comparison of secondary transfer of skin epithelial cells versus vaginal mucous membrane cells by direct contact

In alleged sexual assault and rape cases, the focus has often been to collect samples from the victim's body, for detection of body fluids or skin cells from the offender. But in many cases intimate body samples from the perpetrator(s) can also be informative. However, in cases where the female victim claims vaginal penetration, the defendant may display an alternative explanation to the DNA findings, i.e. that the victim’s skin cells has been secondarily transferred to his penis. We hypothesized that female DNA will be detected in a significantly greater amount on swabs from penis after intercourse than after secondary transfer by skin contact.Fourteen male-female couples were recruited to test the above hypothesis, by collecting penile swabs from 3 specified anatomical locations: Glans, shaft, and the coronal sulcus, after two different situations: Vaginal intercourse and secondary transfer of epithelial cells by skin contact. The results show that penile swabs following intercourse produce significantly higher DNA concentrations than after secondary transfer by skin contact. Our results, indicates which of the anatomical regions is best suited for sampling. The DNA profiling results show a preponderance of female profiles over male profiles following intercourse compared to secondary skin contact.Based on these data, it is possible to make a statistical model to distinguish between samples taken after intercourse and samples taken after secondary transfer by skin contact based on the amount of female DNA and mixture proportion (Mx) between female and male DNA in samples collected from penis swabs.