Background interference from car carpets—the evidential value of petrol residues in cases of suspected vehicle arson

This study was undertaken to test the theory that there is a natural occurrence of petrol on the carpet or carpet mats of motor vehicles that would interfere with the potential determination of arson residues. Part of this study was also to determine what levels of background interference due to the carpet matrix are likely to be encountered in the general population of motor vehicles. The study was conducted in three parts.

• 1.A persistence study was conducted to determine the evaporation and persistence of unleaded petrol on carpet. The results indicate that small volumes of petrol (less than 100 μl) are unlikely to be detected on carpet after a 24 h period. Larger volumes will be detected after this period, but will generally not be detectable after 1 week.
• 2.A known history study was conducted by the insertion of carpet mats, for varying lengths of time, into the driver area of separate vehicles, with subsequent analysis for the presence of petrol. A ‘history’ sheet was completed by the occupants of the vehicles during the insertion periods to record the frequency of contact with petrol, and general usage of the vehicles. The results indicate that petrol will not normally be found on previously uncontaminated carpet mats after a 6-week period of use in a vehicle, however, the occupation and behaviour of the occupants can affect the types of compounds deposited onto the carpet.
• 3.An unknown history study was conducted via the collection of carpet or carpet mat samples from vehicles with an unknown history, and subsequent analysis for the presence of petrol. Six of the 150 samples examined contained petrol. These results indicate that only a small proportion of motor vehicles will exhibit the presence of petrol on carpet or carpet mats, and then only as evaporated petrol.

All of the above findings increase the evidential value of finding significant volumes of fresh or slightly evaporated petrol on carpet products in motor vehicles.     

Adsorption saturation and chromatographic distortion effects on passive headspace sampling with activated charcoal in fire debris analysis

Distortion of the chromatographic profile obtained for hydrocarbons that have been sampled by adsorption onto activated charcoal is a well-known phenomenon. The work reported here helps to better define the causes of chromatographic profile distortion and offers a potential method to avoid chromatographic distortion in some cases through a subsampling technique. The recovery of hydrocarbons from an equimolar mixture was investigated to determine the influence of hydrocarbon concentration on the molar ratios of recovered components. In a one-quart container, hydrocarbon volumes as small as 24 microL (liquid) were sufficient to saturate the surface area available for adsorption on a 99.0 mm2 square of activated charcoal, resulting in significant distortions in the molar ratio and the chromatographic profile of the recovered hydrocarbons. Passive headspace sampling of a similarly small volume of unweathered gasoline spiked onto carpet padding resulted in a significant distortion of the chromatographic profile. The chromatographic profile of the recovered hydrocarbons closely resembled 75% weathered gasoline. Heating the container spiked with unweathered gasoline to evenly distribute the components and then removing a subsample of the carpet padding to a second container for passive headspace analysis greatly reduced the amount of distortion in the resulting chromatogram.     

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.     

An investigation into the presence of petrol on the clothing and shoes of members of the public

First, the clothing and shoes from 29 participants who had recently filled their vehicles with petrol were analysed for any traces of petrol. No traces of petrol were found on any of these items. Secondly, the clothing and shoes from 17 participants who had recently used a petrol-powered lawn mower were also analysed for petrol. Petrol was detected on two pairs of shoes from different participants. Components of petrol were detected on a set of clothing from a third participant, however, there were insufficient components present in this sample to confirm the presence of petrol. No traces of petrol were found on the items from the remaining 14 participants. Thirdly, the clothing from a forecourt attendant, a mechanic and a professional lawn mower were analysed at the end of a number of shifts. Petrol was detected on the upper and lower clothing from the forecourt attendant at the end of one shift. No petrol residues were found on the forecourt attendant after a second shift, or on the mechanic's clothing after two separate shifts or on the professional lawn mower's clothing after three separate shifts. These results can be used to assist the forensic analyst in assessing the chance of finding traces of petrol on clothing and shoes after the wearer has performed common activities that involve petrol.     

Application of forward‐looking infrared (FLIR) imaging from an unmanned aerial platform in the search for decomposing remains

Traditional methods of cadaver detection in outdoor environments include manual ground search, cadaver dogs, and manned aerial reconnaissance during daylight. These methods have limitations; however, a potential low‐cost alternative may be to employ thermal imaging equipment mounted on an unmanned aerial vehicle (UAV) to detect heat emitted by insect and bacterial activity on the decomposing remains. No studies have addressed the influence of wrappings on detection of maggot mass thermal signatures nor assessed thermal detection of smaller body fragments. We addressed these knowledge gaps by utilizing a two‐phase experimental approach to explore thermal detection of carcasses using UAV‐mounted infrared imaging. In Phase 1, pig body fragments were deposited on the surface or shallow buried. In Phase 2, whole pig carcasses were deposited in four conditions: on the surface uncovered, wrapped in plastic or carpet, or buried. Our results demonstrated that observable heat emissions from remains corresponded to peak insect activity during active decay and could be readily detected in uncovered whole carcasses and fragments. Although plastic and carpet wrappings partly impeded detection of insect heat signatures, these materials were clearly detectable themselves because of their contrast to the background ground surface. Thermal signatures of buried partial remains and disturbed gravesoil were also observed; however, the buried whole carcass transitioned to adipocere prior to the decay stage and without any insect colonization or heat signature. These data can inform operational implementation of this technique to complement existing search strategies to offer a robust, low‐cost alternative for use where scene characteristics allow.     

Pyrolysis products of structure fires

Common floor-coverings, carpet, synthetic turf, vinyl flooring and pad (underlay) were exposed to a real-life fire environment consisting of an ordinary combustible fuel load in a room. Samples of the floor-coverings were recovered immediately after extinguishment and subjected to laboratory testing using heated head space and charcoal trap-carbon disulphide extraction. Polyethylene/polypropylene synthetic turf and polyurethane padding were found to present a significant volatile signature after such exposure. In a second test, several floor-coverings were burned in a room fire involving the use of three common petroleum products. None of the floor-coverings presented significant interference to identification of these accelerants in the post-fire debris; however, they were found to generate volatiles which might be mistaken for synthetic blends or specialist solvents. The difficulties and value of reproducing full-scale environments and their effects on combustibles are discussed.     

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.     

Fatal positional asphyxia associated with rollover crashes

Motor vehicle rollover crashes result in complex occupant kinematics with the potential for severe injury. Five cases of fatal asphyxia in occupants suspended from their safety belt upside down after a rollover crash are presented. These fatalities accounted for 13.5% of all motor vehicle related asphyxia deaths in San Diego County over a 10-year period. This study supports previous research noting that incapacitation due to other injuries, alcohol, or obesity may be associated with fatal positional asphyxia due to inversion during rollovers. Safety belts are proven to prevent serious injury in motor vehicle crashes and should always be worn. However, redesign of the buckle could be considered to permit easier release by an occupant. We also suggest that pre-existing heart disease may contribute to the possibility of a fatal asphyxia outcome. Although this is a rare cause of motor vehicle related death, our results suggest that these are potentially preventable deaths.     

Persistence of floor coating solvents.

Using passive headspace concentration as described in ASTM E 1412 and gas chromatographic/mass spectrometric (GC/MS) analysis as described in ASTM E 1618, the author has studied the persistence of solvents in floor coating materials. Both oak and pine flooring boards were tested using stain, stain with polyurethane varnish, and oil finish after a period of ten months and 24 months. The solvents from all three floor-coating substances were easily detectable after 24 months, and showed no signs of diminution when compared with the samples tested earlier. These results point out the need for the submission of comparison samples whenever wood flooring samples are submitted for fire debris analysis in suspected arson cases.     

Detection of ethyl glucuronide in blood spotted on different surfaces

This study aims to show that sensitive detection of ethyl glucuronide in dried blood spotted onto various surfaces after a period of 24h is feasible. At present, there is insufficient information how tightly ethyl glucuronide (EtG) binds to various materials and how easily it can be eluted. 4ml aliquots of blood samples obtained from seven volunteers after consumption of alcoholic beverages were applied to six different surfaces. After drying and a 24h-storage at 20±2°C the samples were re-dissolved in water, and EtG was subsequently analyzed by a LC-MS Paul-type ion trap. A comparison was made between dried and corresponding fluid samples. EtG was detectable in all subjects' samples following consumption of alcohol. EtG was also detectable after a storage time of four weeks at 4°C in whole blood that had been preserved with EDTA. EtG was detectable in all samples dried on different surfaces and its concentration remained relatively constant irrespective of the particular condition of the material. Detection of EtG in blood spots from the scene may indicate recent alcohol consumption in cases where collection of blood remained undone or could not be performed.     

Profiling pythons to combat common illegal wildlife activities

Reptiles are the most common illegally traded vertebrates leading to many species becoming extinct or highly endangered; yet these species receive relatively low publicity and few genetic tests are available. Sought after as unusual pets and trophies, reptilian skin and meat are also valuable commodities, while certain anatomical features are valued in traditional medicinal cultures. The Australian carpet python is a popular target for illegal trade, breeding and export activities. It provides a model example for which to develop forensic markers that will positively impact wildlife criminal investigation and enforcement both in Australia and worldwide. We report on the initial isolation and characterisation of 24 polymorphic Short Tandem Repeat (STR) loci to enable individualisation and paternity testing of carpet pythons. These novel loci have been examined for their polymorphic content, heterozygosity and species specificity. The loci are being arranged into multiplex reactions exhibiting heterozygote balance with subsequent determination of stutter measurements. Allelic frequency databases of native populations are being developed that will allow not only match probabilities but also will potentially predict geographic origin of poached individuals. This profiling system will be subject to rigorous validation for use in legal proceedings.     

The Forensic Implications of Amphetamine Intoxication in Cases of Inflicted Blunt Craniocerebral Trauma

The effects of D‐amphetamine on outcome after blunt craniocerebral trauma are characterized and the potential legal implications discussed. Traumatic brain injury (TBI) was induced under general anesthesia in adult, male Sprague Dawley rats using the impact acceleration model. At 10 min prior to injury, D‐amphetamine (5 mg/kg) or saline vehicle was administered subcutaneously; animals were subsequently assessed over a 7‐day period post‐trauma for motor outcome using a rotarod device. D‐amphetamine treated animals performed significantly better (p < 0.001; ANOVA) than vehicle treated controls on their motor assessment, suggesting that D‐amphetamine exposure prior to injury either is neuroprotective or enhances motor performance. It is possible, therefore, that an individual who has taken amphetamines may function at a better motor level after head trauma than one who has not been exposed to the drug. Future interpretations of the potential effects of amphetamines on TBI should include this possibility.     

Dermal lesions after post mortem petrol-exposure

The effect of post mortem contact of the skin with petrol was investigated in 18 corpses with exposure times between 10 min and 24 h. The earliest onset of skin changes was observed within 2 h of exposure. They consisted of swelling and wrinkling with detachment of the upper layers of the skin (positive Nikolski's sign). Histologically the lesions appeared as non-vital acantholyses located in the prickle-cell layer with formation of intra-epidermal bullae. An influence of age and sex could be excluded, the earlier onset of lesions at 22 degrees C than at 4 degrees C was not statistically significant. These findings prove that post mortem petrol exposure may lead to dermal lesions.     

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.     

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.     

Effect of evaporation and matrix interferences on the association of simulated ignitable liquid residues to the corresponding liquid standard

Identification of an ignitable liquid in fire debris evidence can be complicated due to evaporation of the liquid, matrix interferences, and thermal degradation of both the liquid and the matrix. In this research, liquids extracted from simulated fire debris were compared to the original liquid using multivariate statistical procedures. Neat and evaporated gasoline and kerosene standards were spiked onto nylon carpet, which was subsequently burned. The ignitable liquid residues were extracted using a passive headspace procedure and analyzed by gas chromatography-mass spectrometry. Pearson product moment correlation coefficients, hierarchical cluster analysis, and principal components analysis were used to compare the liquids extracted from the carpet to the corresponding neat liquid. For each procedure, association of the extracts according to liquid type was possible, albeit not necessarily to the specific evaporation level. Of the three procedures investigated, principal components analysis offered the most promise since contributions from matrix interferences were essentially eliminated.     

An enzyme immunoassay for prostate-specific p30 antigen detection in the postcoital vaginal tract

A sandwich enzyme immunoassay test utilising a mouse monoclonal antibody has been adapted for the sensitive detection of the p30 prostatic antigen in semen and in postcoital vaginal swabs. In liquid semen, p30 was still detectable at a 1/1,000,000 dilution, and it could still be detected on vaginal swabs 24 h postcoitus.     

Rapid confirmation of enzyme multiplied immunoassay technique (EMIT) cocaine positive urine samples by capillary gas-liquid chromatography/nitrogen phosphorus detection (GLC/NPD)

A rapid gas-liquid chromatographic (GLC) method was developed for the confirmation of benzoylecgonine (BE) positive urine samples screened by the enzyme multiplied immunoassay technique (EMIT) assay. The procedure is performed by solvent extraction of BE from 0.1 or 0.2 mL of urine, followed by an aqueous wash of the solvent and evaporation. The dried residue was derivatized with 50 microL of pentafluoropropionic anhydride and 25 microL of pentafluoropropropanol at 90 degrees C for 15 min. The derivatizing reagents were evaporated to dryness, and the derivatized BE, and cocaine if present, were reconstituted and injected into the gas chromatograph. The column was a 15-m by 0.2-mm fused silica capillary column, coated with 0.25 micron of DB-1, terminating in a nitrogen phosphorus detector (NPD). Cocaine and the pentafluoro BE derivatives retention times were 3.2 and 2.6 min, respectively. Nalorphine was used as reference or internal standard with a retention time of 4.78 min. The complete procedure can be performed in approximately 1.5 h. The EMIT cutoff between positive and negative urine samples is 300 ng/mL of BE. The lower limit of sensitivity of this method is 25 ng of BE extracted from urine. Validation studies resulted in confirmation of 101 out of 121 EMIT cocaine positive urine samples that could not be confirmed by thin-layer chromatography (TLC). This represents 84% confirmation efficiency.     

The forensic examination of a fire-damaged vehicle.

The Lothian and Borders Police Forensic Science Laboratory was asked to assist in the investigation of a suspected fraudulent insurance claim involving a fire-damaged motor vehicle. This case demonstrates the persistence of fire accelerants when confined, and the reproducible nature of volatiles created from the accelerated burning of a synthetic material.     

Detection of fingermarks by colloidal gold (MMD/SMD)--beyond the pH 3 limit

Dust was investigated for its ability to retain source attribution profiles (SAPs) after chemical exposure. Three distinct sources of the organophosphate pesticide acephate were investigated as a proof-of-concept model. In addition, attribution profiles were created and tested using compounds related to chemical warfare agents (CWAs), specifically VX and G-series agents: O-ethyl methylphosphonothioate (EMPTA), N,N-diisopropylmethylamine (DIPMA), N,N-diisopropylethylamine (DIEA), diisopropylamine (DIPA), diethyl aniline (DEA), diethyl ethyl phosphonate (DEEP), trimethyl phosphite (TMP), dimethyl hydrogen phosphite (DMHP), diethyl hydrogen phosphite (DEHP), triethyl phosphate (TEP), ethyl methylphosphonate (EMPA), and diisopropyl methylphosphonate (DIMP). Dust was collected from a storage shed, aliquots deposited on carpet and loaded with distinct chemical profiles using an exposure chamber and aerosolizer. After a given period of time (1h, 24h, or 72 h), the dust was extracted and its SAP analyzed by gas chromatography-mass spectrometry (GC-MS) and/or liquid chromatography-tandem mass spectrometry (LC-MS/MS). Principal components analysis (PCA) was used to determine the association of dust exposed to the same and different chemical sources. PCA results demonstrate that dust samples exposed to distinct chemical sources are clearly differentiated from one another across all collection times. Furthermore, dust aliquots exposed to the same source can be clearly associated with one another across all collection times. When the CWA-related compounds were subjected to elevated temperature (90°C) conditions, it was found that the signature was stable at the 1h and 24h collections. At 72 h and elevated temperature, larger deviations from the control were observed for some compounds. Elevated pH (10) affected the profile to a lesser degree than elevated temperature. Overall, dust is found to be an effective media for the in situ collection of source attribution profiles.