Forensic Discrimination Research Articles

Forensic Discrimination of Aluminum Foil by SR-XRF and ICP-AES

The application of synchrotron radiation X-ray fluorescence spectrometry (SR-XRF) was investigated for the forensic discrimination of aluminum foil by comparisons of the elemental components. Small fragments (1 x 1 mm) were taken from 4 kinds of aluminum foils produced by different manufactures and used for measurements of the XRF spectrum at BL37XU of SPring-8. A comparison of the XRF spectra was effective for the discrimination of aluminum foils from different sources, because significant differences were observed in the X-ray peak intensities of Fe, Cu, Zn, Ga, Zr and Sn. These elements, except for Zr and Sn in the aluminum foils and NIST SRM1258 (Aluminium Alloy 6011), were also determined by inductively coupled plasma atomic emission spectrometry (ICP-AES). The observed values of Fe, Cu, Zn and Ga in NIST standard samples by ICP-AES showed satisfactorily good agreements with the certified or information values with relative standard deviations from 1.1% for Zn to 6.7% for Ga. The observed values for the aluminum foils by ICP-AES were compared with those by SR-XRF. Correlation coefficients from 0.997 for Cu/Fe to 0.999 for Zn/Fe and Ga/Fe were obtained between the ratio of the elemental concentration by ICP-AES and normalized the X-ray intensity by SR-XRF. This result demonstrates that a comparison of the normalized X-ray intensity is nearly as effective for the discrimination of aluminum foils as quantitative analysis by ICP-AES. Comparisons of the analytical results by SR-XRF allow the discrimination of all aluminum foils using only a 1 mm{sup 2} fragment with no destruction of the samples. (author)

Forensic Discrimination of Tiny Glass Fragments with Non-flat Surface by Trace Elemental Analysis Using LA-ICP-MS

Forensic Discrimination of Tiny Glass Fragments with Non-flat Surface by Trace Elemental Analysis Using LA-ICP-MS

Forensic Discrimination of Yellow in Similarly Colored Single Wool Fibers by Ultraviolet-Visible-Microspectrophotometry and Thin-Layer Chromatography

During the identification of single fiber evidence, color evaluation is one of the most important examinations. Colors are usually first evaluated by ultraviolet-visible-microspectrophotometry (UV-vis-MSP). If possible, thin-layer chromatography (TLC) or high performance liquid chromatography (HPLC) are conducted after the extraction of dyestuffs from the single fiber. In this report, three woolen single fibers were dyed by similarly colored dyes with structurally different yellow acid dyes and were used to evaluate the discriminatory abilities of UV-vis-MSP and TLC.

Discrimination of Grass Hay Samples by DNA Analyses

Grasses are common plant species encountered in botanical evidence because of their wide range of habitats. Presently forensic plant samples are discriminated based on morphological observation, however, some textures occasionally show similar characteristics among different species. In this study, discrimination of grass samples was carried out by comparison of rbcL partial region sequence, which is used as markers for phylogenetic and taxonomic studies. Sequence analyses were performed on 5 commercially available grass hay samples and plant fragments collected from 3 different cowsheds. The rbcL sequences of commercially available grass hay samples were characteristic to each other. All grass samples collected from the same cowshed had identical sequences, and the sequence was characteristic to each cowshed. Furthermore, different parts of the plant body could be analyzed and showed the identical sequences within the same sample. The results suggest that discrimination among grass hay samples was possible by comparison of rbcL sequences and DNA sequences used as phylogenetic and taxonomic markers will be useful for forensic discrimination of plant evidence.

Exploring the Discriminatory Potential of F0 Distribution Parameters in Traditional Forensic Speaker Recognition

Despite its many prima facie attractive properties for Forensic Speaker Recognition, F0 is regarded as having limited forensic value due to its large within-speaker variability. However, its forensic use to date has been limited mostly to its long-term mean and standard deviation. This paper examines the discriminatory potential, within a Likelihood Ratio-based approach, of additional parametric features from the distribution of long-term F0: its skew, kurtosis, modal F0 and modal density. Motivated by the observation that the shape of the long-term F0 distribution shows less within-speaker occasion-to-occasion difference, we report a forensic discrimination experiment with non-contemporaneous speech samples from 201 male Japanese speakers. Using a multivariate Likelihood Ratio as discriminant distance with the six LTF0 distribution parameters, an equal error rate of 10.7% is obtained from 201 target and 80400 non-target trials. We also investigate how the EER degrades as a function of amount of voiced speech.

Forensic discrimination of glass using cathodoluminescence and CIE LAB color coordinates: A feasibility study

Cathodoluminescence (CL) spectroscopy has been shown to be useful for differentiating typical evidentiary glass samples. CL occurs when a surface is bombarded with an electron beam as in scanning electron microscopy and most of this luminescence is in the visible range. In effect, CL imparts color to colorless evidence and as a result, proven methods of forensic color analysis can be applied. In this work, spectral data dimensions were reduced to three and plotted in the CIE LAB color space. This approach allows for incorporation of uncertainties generated principally by intra-sample variation. NIST glass standards were used for method development and validation while potential case applications were studied with collections of window, consumer, and auto headlamp glasses. Using refractive index as the initial grouping variable, all of the window and consumer glasses were differentiated as were 6 of 10 automobile headlamp glasses. The potential advantages of CL include low cost instrumentation, its non-destructive nature, and ease of operation. The current limitations of CL in this context are the lack of databases and standards and the relatively low resolution of typical CL spectra.

Real-time contaminant detection and classification in a drinking water pipe using conventional water quality sensors: Techniques and experimental results

Accurate detection and identification of natural or intentional contamination events in a drinking water pipe is critical to drinking water supply security and health risk management. To use conventional water quality sensors for the purpose, we have explored a real-time event adaptive detection, identification and warning (READiw) methodology and examined it using pilot-scale pipe flow experiments of 11 chemical and biological contaminants each at three concentration levels. The tested contaminants include pesticide and herbicides (aldicarb, glyphosate and dicamba), alkaloids (nicotine and colchicine), E. coli in terrific broth, biological growth media (nutrient broth, terrific broth, tryptic soy broth), and inorganic chemical compounds (mercuric chloride and potassium ferricyanide). First, through adaptive transformation of the sensor outputs, contaminant signals were enhanced and background noise was reduced in time-series plots leading to detection and identification of all simulated contamination events. The improved sensor detection threshold was 0.1% of the background for pH and oxidation–reduction potential (ORP), 0.9% for free chlorine, 1.6% for total chlorine, and 0.9% for chloride. Second, the relative changes calculated from adaptively transformed residual chlorine measurements were quantitatively related to contaminant-chlorine reactivity in drinking water. We have shown that based on these kinetic and chemical differences, the tested contaminants were distinguishable in forensic discrimination diagrams made of adaptively transformed sensor measurements.

Forensic Discrimination of Steel Wires by Quantitative Elemental Analysis with ICP-MS

The application of inductively coupled plasma mass spectrometry (ICP-MS) in the determination of the concentrations of trace elements in steel wires was investigated for the forensic discrimination of wires with different origins; the discrimination is carried out by comparing elemental compositions. Approximately 5 mg of a chip taken from the wire was accurately weighed and dissolved in a mixture of 100 μl HCl and 100 μl HNO3 by heating at 80°C for 30 min. Following the addition of 100 μl of 5 μg/ml Y as an internal standard and 200 μl of 7M HCl, the matrix iron in the solution was removed by extraction with 200 μl MIBK. This extraction was repeated twice, and 300 μl of the aqueous phase was heated at 150°C for 1 h after the addition of 250 μl H2SO4. This solution was diluted to 25 ml by 1% HNO3, and then the solution was used to determine the concentrations of Cr, Mn, Ni and Cu by ICP-MS. The measured values of these elements in NIST 16f (Steel Basic Open-Hearth) showed satisfactory good agreement with the certified values with RSDs from 1.0 to 2.1%. A comparison of the concentrations of the four elements determined by using the present method can be carried out to differentiate among the 21 possible pairs that can be formed from 7 wires produced by different manufacturers.

Forensic discrimination of blue ballpoint pen inks based on thin layer chromatography and image analysis

This article aims to provide a new and fast method for differentiation of inks on a questioned document. The data acquisition was carried out by designing specific image analysis software for evaluating thin layer chromatograms (TLC-IA). The ink spot was extracted from the document using methanol and separated by TLC using plastic sheet silica gel 60 without fluorescent indicator, and a mixture of ethyl acetate, ethanol, and water (70:35:30, v/v/v) as mobile phase. To discriminate between different pen inks, new software was designed on the basis of intensity profile of red, green, and blue (RGB) characteristic. In practice, after development of chromatogram, the chromatograms were scanned by ordinary office scanner, intensity profiles of RGB characteristics on the development straight of each sample were produced and compared with the mentioned software. RGB profiles of ballpoint inks from various manufacturers showed that the patterns in most cases were distinctly different from each other. This new method allowed discriminating among different pen inks with a high reliability and the discriminating power of 92.8%. Blue ballpoint pen inks of 41 different samples available on the local market were successfully analyzed and discriminated.

Forensic Discrimination of Sheet Glass Exposed to High Temperature by the Determination of Trace Impurities Using ICP-MS

The effect of heating on the refractive index (RI) and trace elemental compositions of glass was investigated in order to develop an accurate discrimination method of glass fragments exposed to the high temperature of fire on illegal entrance into a crime scene for robbery. Fragments taken from 5 different sheet glasses were subjected to RI measurement and analysis of trace elements using ICP-MS before and after heating at 764 degrees C for 2 min. The difference in the RI between the heated and non-heated fragments ranged from 0.0012 to 0.0015, which corresponds to 6 times more than the variation of the RI within a pane of glass. In contrast, profiles of 10 elements (Co, Rb, Sr, Zr, Mo, Ba, La, Ce, Nd and Pb) in glass exhibited no significant difference between the heated and non-heated ones. In conclusion, the forensic discrimination of glass fragments must be performed not by RI measurement, but by analysis of the elemental compositions when glass evidence could be exposed to the high temperature of fire.

Determination of Sex for the 12th Thoracic Vertebra by Morphometry of Three‐dimensional Reconstructed Vertebral Models

Thirty-three linear measurements and two ratios were derived from 102 12th thoracic vertebrae of the Digital Korean database at the Catholic Institute for Applied Anatomy. Of 35 linear traits, 23 were sexually dimorphic. We created 23 discriminant function equations that predicted sex with 62.7-85.3% accuracy. The analysis using combinations of two factors gave higher accuracies: most equations with accuracies over 80% included at least one measurement involving the coronal diameter of the vertebral endplate. Using stepwise method of discriminant function analysis, three variables predicted sex with 90.0% accuracy: the coronal diameter of the superior endplate of the vertebral body, the ratio of anterior to middle height of the body, and the length of the left mammillary process and pedicle. Coronal dimensions of the vertebral body represented the major sex difference. These equations will help forensic discrimination of the sex of this vertebra among Koreans.

Multiplex Mutagenically Separated Polymerase Chain Reaction Assay for Rapid Detection of Human Mitochondrial DNA Variations in Coding Area

Recently, it has been recognized that information in the mitochondrial DNA (mtDNA) coding region can provide additional forensic discrimination with respect to the standard typing of the D-loop region, increasing the forensic power of mtDNA testing, which is sometimes rather limited. In the present study, we simultaneously typed ten single nucleotide polymorphisms (SNP) in the coding region by use of mutagenically separated polymerase chain reaction (MS-PCR) in the Chinese Chengdu population. This technique, in which different-size allele-specific primers were used, specifically amplified both alleles of mtDNA in the same reaction. Subsequent gel electrophoresis showed ten of the allelic products of different loci. Using multiplex MS-PCR, 30 primers were added simultaneously into one reaction tube to identify ten SNPs. The mtDNA variations of 160 individuals from the Chinese Chengdu population were examined and classified into 18 haplotypes. The multiplex MS-PCR method is suitable for large-scale screening studies of mtDNA variability because it is both rapid and economical.

Analysis of Trace Element Compositions in Adhesive Cloth Tapes Using High-Energy X-Ray Fluorescence Spectrometer with Three-Dimensional Polarization Optics for Forensic Discrimination

高エネルギーX線を励起源とする3次元偏光光学系蛍光X線分析装置を用いて，犯罪に利用されることが多い布粘着テープの異同識別法の開発を試みた．検討の結果，識別に最適な分析条件は以下のとおりである．2次ターゲットとしてRhとAl2O3を用い，測定時間はそれぞれ300秒と600秒，分析に用いた元素はCa，Ti，Cr，Mn，Fe，Ni，Zn，Sr，Zr，Nb，Mo，Sb，Ba，Pbの14元素である．方法の有効性を検証するため，市販の布粘着テープ17社31試料へ応用した．糸密度と蛍光X線（XRF）スペクトルの14元素のピーク強度の組み合わせにより，31試料中29試料をうまく識別できることが分かった．識別できなかった2試料は同一起源のものと思われた．このように蛍光X線分析を用いる本方法は，非破壊で迅速，簡便であることから法科学的分析法として実用性が高いことが分かった．

Lower limits of detection of synchrotron radiation high-energy X-ray fluorescence spectrometry and its possibility for the forensic application for discrimination of glass fragments

Synchrotron radiation high-energy X-ray fluorescence (SR-XRF) analysis utilizing 75.5 keV X-ray radiation from beam-line BL37XU at Super Photon Ring 8 GeV (SPring-8), a third-generation synchrotron facility, was found to have advantages for forensic discrimination of glass samples. The lower limits of detection (LLD) for calibration curves were at the picogram level for Ba, Ce, and Sm and at the 10 pg level for Sr, Zr, Sn, and Hf. The spectrum of NIST SRM 612 glass reference material demonstrated K-line peaks of 31 elements including rare-earth elements, and the relative standard deviations (R.S.D.) of all the measured elements except Ca were less than 9.7%. Fragments of collected sheet glass were used as samples for investigating the application of this technique to forensic analysis. Several trace elements such as Pb, Rb, Sr, Zr, La, Ce, and Hf were detected in the spectra of the samples, and these elements could be used as indexes to characterize the glass samples. But the “lower limits of detection (LLD)” of each element were not examined enough. In this report, these limits by synchrotron radiation X-ray spectrometry were clarified. By these results, this technique should provide an effective approach to the nondestructive discrimination of small glass fragments in the field of forensic science.

Passport Examination by Polarized Infrared Spectra

In this study, a new nondestructive technique for passport examination is proposed. In this technique, linearly polarized light is used to measure Fourier transform infrared (FT-IR) reflectance spectra of films on the biographical data page. Thirty genuine and thirty-five counterfeit Japanese passports and five marketed films pasted on name cards were examined. The measured spectra were analyzed as follows. The absorption spectra were obtained by the Kramers-Kronig transformations of reflectance spectra. The peak ratios were then calculated from the absorption spectra by adding the peak areas at 1126 and 1263 cm(-1) and dividing the result by the peak area at 1727 cm(-1). When nonpolarized light was used, the samples could not be distinguished by comparing the peak ratios. However, when polarized light was used, they were successfully distinguished by the comparison. Therefore, polarized light is useful for the forensic discrimination of passport films by the measurement of FT-IR spectra.

Forensic Discrimination of Trace Fragments of Photocopied Materials

The forensic discrimination of photocopied characters was examined by the combination of data, such as morphological observations and elemental analyses by SEM/EDX, resin ingredient analyses by Pyr-GC/MS and microscopic FT-IR, and organic additives analyses by HPLC. As an obtained result, a significant morphological difference was observed between each sample, and also characteristic elements, for instance Si, Fe, Cu and Cr, were detected by EDX analyses. The result obtained from Pyr-GC/MS showed that the utilized resin consisted of a styrene-type resin, and spectra obtained by micro FT-IR analysis; these resins were divided to three groups: a styrene/methylmetacrilate copolymer was used in samples 1 and 2. In contrast with this result, a styrene/acryle/epoxy copolymer resin was used in samples 3 and 4. In order to analyze organic additives, part of character was subjected to an extractor by acetonitrile, and HPLC was conducted. Comparisons of HPLC chromatograms of extractives from a part of the character on the examined four different kinds of photocopies, significant difference were observed between them. The protocol established by this examination could completely discriminate the 4 photocopied materials. This procedure was applied to an actual blackmail case. The character on the blackmail and burned dust of the paper existed in deposited soils in front of the suspect's house; their similar character was clarified by this analytical protocol. This result reinforced an investigation by information provided from a scientific evidence examination.

Forensic Discrimination of Heated and Non-Heated Sheet Glasses by Analysis of Trace Impurities Using SR-XRF

The application of trace impurity analysis using synchrotron radiation X-ray fluorescence spectrometry (SR-XRF) was investigated for the forensic discrimination of heated and non-heated sheet glasses. Each of 5 sheet glasses produced by 3 domestic manufacturers was divided into 2 groups, one of which was subjected to RI measurement and elemental analysis by SR-XRF after heating at 764°C for 2 minutes while the other was without heating. All of the heated glasses provided lower RI values than those of non-heated ones. The difference in RI between the heated and non-heated glasses ranged from 0.0012 to 0.0015, which was 6∼7 times larger than the variation of RI within a pane of sheet glass. As a result of the elemental analysis of 5 non-heated glasses by SR-XRF, the X-ray intensities of impurity elements, such as Rb, Sr, Zr, Ba, La and Ce, were found to be considerably different among the different glasses. All of 10 pairs among 5 non-heated glasses could be successfully discriminated by comparisons of 4 kinds of X-ray intensity ratios (SrKα/RbKα, ZrKβ/RbKα, BaKα/CeKα, LaKα/CeKα). No significant difference was recognized between the analytical results of the non-heated glasses and those of heated ones by the t-test with a significance level of 1%. It is concluded that trace impurity analysis using SR-XRF is useful for the correct discrimination of heated and non-heated glass fragments, whereas the comparison of only RI can result in false differentiation.

Preliminary Studies on Observation of Pollen Morphology by Scanning Electron Microscope for Forensic Discrimination

The use of a scanning electron microscope (SEM) for forensic pollen analysis was examined as a preliminary study on pollen samples collected from twenty-seven species in general public areas. Pollen samples were air-dried and coated with gold without any pre-treatment which were conventionally performed to remove oil and dewatering. The shapes of pollen grains were observed at magnification of between ×1500 and ×3000, and sculptures were at ×15000. Samples were grouped into three by aperture types, and subdivided by sculptures as the result of observations. Pollens of different families in the same subdivision were distinguishable from the careful observations of details. Pollens of the same genera were grouped in the same subdivisions. It was clarified that use of SEM without any pre-treatment has a high potential for the forensic discrimination of pollen as evidence.

Forensic Discrimination of Steel Wire by Determination of Trace Elements with ICP-AES

The application of inductively coupled plasma atomic emission spectrometry (ICP-AES) to the determination of trace elements in steel wires was investigated for the forensic discrimination of wires produced by different manufacturers based on comparing the elemental composition. About 50 mg of a wire sample was accurately weighed and dissolved into a mixture of 1 mL of HCl and 1 mL of HNO3 by heating at 80°C for 30 minutes, followed by dilution to 10 mL after the addition of a Y solution as an internal standard. Five elements (P, Cr, Mn, Ni and Cu) in the solution of samples prepared as described above were determined using standard solutions for calibration containing the same concentration of Y and reagents as the sample solution. The analytical results of the five elements in NIST Standard Reference Material 16f (Steel Basic Open-Hearth) showed satisfactorily good agreement with the certified values, having relative standard deviations from 0.6% for Ni to 1.2% for P. All of 21 pairs among 7 kinds of wire samples could be discriminated by comparing the concentrations of five elements obtained by the present method.

Profiling 627 Mitochondrial Nucleotides via the Analysis of a 23-Plex Polymerase Chain Reaction by Liquid Chromatography−Electrospray Ionization Time-of-Flight Mass Spectrometry

We present a rapid and informative mitochondrial DNA profiling system, which has high forensic impact. The assay is based on the analysis of a 23-plex PCR by ion-pair reversed-phase high-performance liquid chromatography online hyphenated to electrospray ionization time-of-flight mass spectrometry (ICEMS). In a single 25-min run, an overall number of 627 nucleotide positions were screened. The vast majority of observed sequence variations were explainable by alterations of the allelic states of the 23 target SNPs, which were selected on their ability to increase forensic discrimination within West Eurasian populations. Within an Austrian population sample comprising 90 unrelated men, 14 different, nontarget SNP-related sequence variations--13 base substitutions and 1 deletion--were detected by ICEMS and confirmed by sequencing. All amplified sequences were located outside of the routinely sequenced hypervariable segments (HVS-I and HVS-II) of the noncoding control region. Accordingly, the genetic information obtained by the 23-plex PCR-ICEMS assay could be combined with HVS-I/HVS-II sequencing results to one highly discriminating mtDNA profile, which covered approximately 7.5% of the total mtDNA genome. With the 23-plex PCR-ICEMS assay, DNA mixtures were detected and the allelic ratios were accurately quantified. The observed robustness and sensitivity underlined the practical applicability of the assay in forensic science, which was proven by typing eight representative casework samples.