Identification and Comparison of Electrical Tapes Using Instrumental and Statistical Techniques: II. Organic Composition of the Tape Backing and Adhesive*

Abstract: The microtexture and elemental composition of the backing of electrical tapes have been shown to be highly discriminating. In this study, the organic composition of electrical tape was evaluated as a complementary means of distinguishing tape brands. The backing and adhesive of 72 rolls of electrical tape were analyzed via Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR FTIR) and discriminant analysis was used to classify all samples by brand. Generally, the accuracy for FTIR data (88–99%) was higher than that for elemental data (86–94%). FTIR spectra from the adhesive layer were the most discriminating. In separate studies, two fragments of blast-damaged tape were correctly assigned to their brand of origin and discriminant analysis was used to quantitatively associate or exclude tape samples from two bombing cases.     

Fingerprints and DNA: STR typing of DNA extracted from adhesive tape after processing for fingerprints

An exhibit that is often received for examination in cases of robbery or terrorist activity is adhesive tape. This type of exhibit can often, but not always, be successfully processed for fingerprints. The question arises whether or not it is possible to extract and type DNA after the tape has been sequentially processed for fingerprints. In this work, various donors left fingerprints on the adhesive side of tapes. The tapes were then sequentially processed for fingerprints using an alternate light source, cyanoacrylate fuming, and staining with BY-40 and then crystal violet. DNA was subsequently successfully extracted, amplified and typed for six STR loci.     

Chemical fingerprinting of adhesive tapes by GCMS detection of petroleum hydrocarbon products

Pressure-sensitive adhesive tapes often represent key evidence of crimes such as assault, rape or homicide; thus, the development of analytical techniques able to contribute to a detailed characterization of these materials is of forensic importance. The gas chromatography-mass spectrometry (GCMS) analysis of the solvent extractable fractions of a suite of electrical and gaffer adhesive tapes spanning a range of colors and manufacturers identified a number of petroleum-derived hydrocarbons. Molecular and isotopic analyses of hydrocarbon constituents of complex materials have found wide analytical utility including the forensic investigation of oil spills and arson. Here, we investigate the utility of these techniques for characterizing the hydrocarbon composition of pressure-sensitive adhesive tapes for forensic correlation purposes. Subtle distinction of tape samples was evident in the GCMS distribution of several hydrocarbon groups including alkyl-naphthalenes, hopane and sterane biomarkers. Linear discriminant analysis of the abundances of these products provided high level differentiation of tape manufacturer. The distinction of different adhesive tape samples was further extended by measurement of their stable carbon isotopic values. The molecular and isotopic differences of the petroleum content of tapes are consistent with the use of different petroleum materials used in the manufacturing process and demonstrate the benefits of the combined use of complementary oil hydrocarbon characterization approaches. This study reveals the forensic potential of using established petroleum characterization methods for characterizing materials with a petroleum-derived hydrocarbon element.     

3种提取胶带粘面汗潜指印中DNA的方法比较

目的比较胶带粘面汗潜指印中DNA提取的方法。方法分别采用硅珠法、QIAMicrokit法、硅珠-QIAMicrokit法提取胶带粘面的汗潜指印中DNA,STR复合扩增,荧光电泳检测。结果用QIAMicrokit法、硅珠-QIAMicrokit法提取胶带粘面汗潜指印中DNA,检测成功率分别为21%和36%。硅珠法检测未获成功。结论硅珠-QIAMicrokit法提取胶带粘面汗潜指印中的DNA比QIAMicrokit法,检验时间更短,检测成功率更高。     

Background survey of polyethylene in the Australian Capital Territory – A demonstration of variability in isotopic abundance values and their application to forensic casework

Plastics including adhesive tapes, cable ties, and packaging are common evidence types encountered in forensic investigations and casework. Traditional examination techniques such as Fourier Transform Infrared (FTIR) spectroscopy lack specificity and are unable to discern differences within the same polymer structures leaving the analyst with a generic identification. High quality manufacturing methods further amplify the limitations in detecting variability between samples. Isotope Ratio Mass Spectrometry (IRMS) has been shown to be a valuable technique in further discriminating plastics. Discrimination is achieved by analysing the relative abundances of stable isotopes within a sample, with differences detected in isotope ratios possibly attributed to the source of raw materials and fractionation during the manufacturing process. A survey of cling wraps and re-sealable zipper storage bags collected in the Australian Capital Territory was undertaken to assess the variability in carbon and hydrogen isotope ratios of different brands and samples. The results of this research are discussed, particularly with respect to within and between brand trends, and a case study is presented as an example of the value of including IRMS in a casework context.     

透明胶带的厚度检验

目的研究不同品牌透明胶带的区分方法。方法利用测厚仪对35种不同品牌透明胶带的厚度进行检验,并对所得数据进行统计分析。结果 35种品牌透明胶带组成的595组样品对中有458组可以区分,区分率为77.0%。结论厚度检验法能够在一定程度上区分不同品牌的透明胶带,厚度检验结果可与化学成分检验相互佐证,使得鉴定结论更加准确可靠,为法庭科学领域透明胶带物证的区分提供了一种预检验方法。     

Analysis of pressure sensitive adhesive tape: I. Evaluation of infrared ATR accessory advances

Attenuated total reflection (ATR), also known as internal reflection spectroscopy (IRS), is a forensically accepted method for infrared (IR) analysis of pressure sensitive adhesive tapes. Advancements of ATR accessories in the last decade have provided the forensic examiner several ATR methods to choose from. These accessories offer a variety of ATR crystal choices with a variety of prices and capabilities. Four different types of pressure sensitive adhesive tapes including duct tape, electrical tape, packaging tape and office tape have been used to compare six different ATR methods. Each of the methods tested offers both benefits and limitaltions which must be considered for the type of sample to be analyze. The intent of this paper is to assist the reader in better understanding ATR techniques, the many differences among currently available ATR accessories and how the method is applied to the analysis of pressure sensitive adhesive tape.     

Differentiation of Cosmetic Foundation Creams Using Attenuated Total Reflection Fourier-Transform Infrared Spectroscopy: A Rapid and NonDestructive Approach in Trace Evidence Analysis

Cosmetic foundation creams are encountered as evidentiary material in criminal investigations, particularly in cases related to sexual and physical assault against women. Analyzing foundation cream exhibit is a challenging task as the exhibit is recovered in trace quantity with similar hue. In the present study, ATR FTIR spectroscopy which is a rapid, nondestructive, sensitive, reliable, and safe alternative to other analytical techniques has been used to differentiate 31 cosmetic foundation creams belonging to 23 different brands supported by chemometric methods such as principal component analysis (PCA) and linear discriminant analysis (LDA). The discriminating power of visual analysis is found to be 98.0%, while PCA and LDA further increased the discriminating power to 99.3% and 100%, respectively. The blind test is conducted with three unknown samples (pretended to be unknown to the analyst), which were correctly linked with their respective source. Further, the effect of substrate such as tissue paper (dry and wet) and white cotton cloth during sample analysis are also examined to simulate the actual forensic casework conditions. The stains on substrates could be identified and linked to its parent product as well. The reported method provides significant results for the differentiation of cosmetic foundation creams.     

Discriminating red spray paints by optical microscopy, Fourier transform infrared spectroscopy and X-ray fluorescence

Red spray paints from different European suppliers were characterised to determine the discriminating power of a sequence of analysing techniques. A total of 51 red spray paints were analysed with the help of three techniques: (1) optical microscopy, (2) Fourier transform infrared spectrometry and (3) X-ray fluorescence. Infrared spectra were classified according to binder type, filler and pigment composition and a searchable spectral library was created. Due to the difference in the elemental composition of spray paints, a further discrimination was possible. The microscopic analysis was not taken into consideration for classification purposes. The structure of the substrate under a paint coating strongly affects the surface characteristics of this spray paint. Together with the spectral library, a database of information of spray paints was build.     

胶带粘面手印荧光显现剂的研发与应用

目的根据胶带粘面上潜在手印的特点,利用染料和潜手印的理化性质,研究开发胶带粘面手印荧光显现剂。方法在各种胶带粘面上显现潜在手印,并与常规的碳素墨水染色法进行比较。结果在长波紫外线照射下手印呈黄色明亮荧光,手印纹线清晰、连贯,基本不受手印遗留时间、客体表面颜色和性质的影响。结论胶带粘面上的汗潜手印和血潜手印用荧光显现剂显现效果优于碳素墨水染色法,在实际案件的侦破中有较好的应用前景。     

Identification of pressure-sensitive adhesive polypropylene tape

Identification of colorless, transparent, pressure-sensitive adhesive polypropylene tape (PP tape) was performed using infrared absorption spectrometry (IR) and pyrolysis gas chromatography mass spectrometry (Py-GC/MS) to determine the pressure-sensitive adhesive. Twenty different products of colorless, transparent PP tapes were examined in this study, and the results of analysis of IR spectra and Py-GC/MS were classified into twelve groups. In addition, the tapes were classified into 14 groups on the basis of IR measurement of release agent present in the backside. The results indicate that colorless, transparent PP tapes can be distinguished in terms of manufacturer, thereby demonstrating that this method of identifying colorless, transparent PP tape is effective. Moreover, the method was applied to the analysis of an actual forensic sample.     

Discrimination of document paper by XRF, LA–ICP–MS and IRMS using multivariate statistical techniques

The purpose of this study was to evaluate the potential of inorganic analysis techniques for the discrimination of document (multipurpose office) paper. A set of 25 different multipurpose office papers from the European market was used for comparison. It appeared that for the single techniques LA–ICP–MS had the highest overall discriminating power. Despite its lower sensitivity, XRF also showed good discriminating power but the correlation with LA–ICP–MS is high. The combination of LA–ICP–MS and IRMS provides a powerful and strongly discriminating set of techniques.     

DNA Recovery From Tape-Lifting Kits: Methodology and Practice

In the case of suspicious deaths, the technique of 1:1 taping is often used in Belgium. It consists of affixing a large number of adhesive tapes to the body of the victim. It is conventionally aimed at obtaining microtraces (e.g., fibers, hair) and is usually not used for DNA analysis. However, in some cases, DNA analysis of certain areas of interest identified on the 1:1 taping material can offer a last resort solution. The four-step method that is described in this article involves the selection of areas of interest on the body (Step 1), the selection of the corresponding tapes (Step 2), the decontamination of the tapes (Step 3), the selection of areas of interest on the tapes, for DNA sampling (Step 4). The method is illustrated by its successful application in four murder cases. In each case, DNA profiles of good quality could be identified, including profiles of persons different from the victim.     

The spectroscopic detection of exogenous material in fingerprints after development with powders and recovery with adhesive lifters

The application of powders to fingerprints has long been established as an effective and reliable method for developing latent fingerprints. The powders adhere to the ridge pattern of the fingerprint only, thus allowing the image to be visualised. Fingerprints developed in situ at a crime scene routinely undergo lifting with specialist tapes to facilitate subsequent laboratory analysis. As with all recovered evidence these samples would be stored in evidence bags to allow secure transit from the scene to the laboratory and also to preserve the chain of evidence. In this paper, the application of Raman spectroscopy for the analysis of exogenous material in latent fingerprints is reported for contaminated fingerprints that had been treated with powders and also subsequently lifted with adhesive tapes. A selection of over the counter (OTC) analgesics were used as samples for the analysis and contaminated fingerprints were deposited on clean glass slides. The application of aluminium or iron based powders to contaminated fingerprints did not interfere with the Raman spectra obtained for the contaminants. In most cases background fluorescence attributed to the sebaceous content of the latent fingerprint was reduced by the application of the powder thus reducing spectral interference. Contaminated fingerprints developed with powders and then lifted with lifting tapes were also examined. The combination of these two techniques did not interfere with the successful analysis of exogenous contaminants by Raman spectroscopy. The lifting process was repeated using hinge lifters. As the hinge lifters exhibited strong Raman bands the spectroscopic analysis was more complex and an increase in the number of exposures to the detector allowed for improved clarification. Raman spectra of developed and lifted fingerprints recorded through evidence bags were obtained and it was found that the detection process was not compromised in any way. Although the application of powders did not interfere with the detection process the time taken to locate the contaminant was increased due to the physical presence of more material within the fingerprint. The presence of interfering Raman bands from lifting tapes is another potential complication. This, however, could be removed by spectral subtraction or by the choice of lifting tapes that have only weak Raman bands.     

Forensic utility of carbon isotope ratio variations in PVC tape backings

Forensic interest in adhesive tapes with polyvinyl chloride (PVC) backings (electrical tape) derives from their use in a variety of illicit activities. Due to the range of physical characteristics, chemical compositions, and homogeneity within a single roll of tape, traditional microscopic and chemical analyses can offer a high degree of discrimination between tapes, permitting the assessment of potential associations between evidentiary tape samples. The carbon isotope ratios of tapes could provide additional discrimination among tape samples. To evaluate whether carbon isotope ratios may be able to increase discrimination of electrical tapes, particularly with regards to different rolls of tape of the same product, we assessed the δ(13)C values of backings from 87 rolls of PVC-based black electrical tape (~20 brands, >60 products) Prior to analysis, adhesives were removed to prevent contamination by adhering debris, and plasticizers were extracted because of concern over their potential mobility. This result is consistent with each of these tapes having approximately the same plasticizer δ(13)C value and proportion of carbon in these plasticizers. The δ(13)C values of the 87 PVC tape backings ranged between -23.5 and -41.3 (‰, V-PDB), with negligible carbon isotopic variation within single rolls of tape, yet large variations among tape brands and tape products. Within this tape population, carbon isotope ratios permitted an average exclusion power of 93.7%, using a window of +/-0.3‰; the combination of carbon isotope ratio measurement with additional chemical and physical analyses raises the discrimination power to over 98.9%, with only 41 out of a possible 3741 pairs of tape samples being indistinguishable. There was a linear relationship between the δ(13)C value of tape backings and the change in δ(13)C value with the extraction of plasticizers. Analyses of pre- and post-blast tape sample pairs show that carbon isotope signatures are within 0.3‰ of pre-blast values, indicating that carbon isotope values are largely preserved during an explosion.     

Selection of an adhesive tape suitable for forensic fiber sampling

Five commercial adhesive tapes were tested for fiber uptake and saturation, for recovery and for ease of analysis. On the basis of the results, a high tack adhesive tape has been selected to be used for forensic fiber sampling. This adhesive tape is used as sampling material in two different micro trace kits. The first tape lifting kit is used mainly for the sampling of cars and the second is a 1:1 tape lifting kit for the collection of fibers on a corpse.     

Discrimination of paper-based kraft tapes using Fourier transform of transmitted light images

This study focused on two-dimensional fast Fourier transform (2D-FFT) as a new technique for the discrimination of kraft tapes, which is a kind of adhesive packing tape. The 2D power spectrum (2D-PS) obtained by applying 2D-FFT to an image enables us to obtain information about the spatial periodicity, even if the periodicity is invisible within the image. However, in the case of kraft tape, peaks in the 2D-PS are too unclear to determine its periodicity. We developed novel analytical image processes combined with 2D-FFT. 2D-FFT was applied to 50 randomly selected areas in a transmitted light image of kraft tape. The 2D-PSs were calculated from each area without applying a logarithmic transformation, accumulated, and processed by the removal of the area surrounding the center, and finally normalized for visualization. These processes enhanced the peaks and eliminated local variations. Through an intra-roll comparison, the 2D-PSs collected from a roll were similar in the location of the peaks and in their patterns at low frequency area. Using an inter-roll comparison, the 2D-PSs from 50 commercially available brand-name products were classified into 26 groups based on these peaks and patterns. All results demonstrate that this method, which is convenient, rapid, and non-destructive, could be a valuable tool for the identification of kraft tapes.     

短波紫外反射照相显现胶带粘面潜在指印

目的研究胶带粘面上指印的提取方法。方法用短波紫外照相的方法对各种胶带粘面的指印进行拍照提取。结果从理论上解释了短波紫外照相拍照提取胶带粘面上指印的原理,从实践上为短波紫外照相法提取胶带粘面上指印提供技术方法和技巧。结论为胶带粘面指印的提取提供了一种新的方法。     

Atomic force microscopic investigation of commercial pressure sensitive adhesives for forensic analysis

Pressure sensitive adhesive (PSA), such as those used in packaging and adhesive tapes, are very often encountered in forensic investigations. In criminal activities, packaging tapes may be used for sealing packets containing drugs, explosive devices, or questioned documents, while adhesive and electrical tapes are used occasionally in kidnapping cases. In this work, the potential of using atomic force microscopy (AFM) in both imaging and force mapping (FM) modes to derive additional analytical information from PSAs is demonstrated. AFM has been used to illustrate differences in the ultrastructural and nanomechanical properties of three visually distinguishable commercial PSAs to first test the feasibility of using this technique. Subsequently, AFM was used to detect nanoscopic differences between three visually indistinguishable PSAs.     

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.