Digital camera identification using PRNU: A feature based approach

Source camera identification is one of the emerging field in digital image forensics, which aims at identifying the source camera used for capturing the given image. The technique uses photo response non-uniformity (PRNU) noise as a camera fingerprint, as it is found to be one of the unique characteristic which is capable of distinguishing the images even if they are captured from similar cameras. Most of the existing PRNU based approaches are very sensitive to the random noise components existing in the estimated PRNU, and also they are not robust when some simple manipulations are performed on the images. Hence a new feature based approach of PRNU is proposed for the source camera identification by choosing the features which are robust for image manipulations. The PRNU noise is extracted from the images using wavelet based denoising method and is represented by higher order wavelet statistics (HOWS), which are invariant features for image manipulations and geometric variations. The features are fed to support vector machine classifiers to identify the originating source camera for the given image and the results have been verified by performing ten-fold cross validation technique. The experiments have been carried out using the images captured from various cell phone cameras and it demonstrated that the proposed algorithm is capable of identifying the source camera of the given image with good accuracy. The developed technique can be used for differentiating the images, even if they are captured from similar cameras, which belongs to same make and model. The analysis have also showed that the proposed technique remains robust even if the images are subjected to simple manipulations or geometric variations.     

A Bayesian Approach to Age‐at‐Death Estimation from Osteoarthritis of the Shoulder in Modern North Americans

Osteoarthritis (OA) is a marker of degeneration within the skeleton, frequently associated with age. This study quantifies the correlation between OA and age‐at‐death and investigates the utility of shoulder OA as a forensic age indicator using a modern North American sample of 206 individuals. Lipping, surface porosity, osteophyte formation, eburnation, and percentage of joint surface affected were recorded on an ordinal scale and summed to create composite scores that were assigned a specific phase. Spearman's correlation indicated a positive relationship between each composite score and age (right shoulder = 0.752; left shoulder = 0.734). Transition analysis revealed a tendency toward earlier degeneration of the right shoulder. Bayesian statistics generated phase‐related age estimates based on highest posterior density regions. Best age estimates were into the seventh decade at the 90th and 50th percentile. The proposed method supplements traditional techniques by providing age estimates beyond a homogenous 50+ age cohort.     

A comparison of plastic cable ties based on physical,chemical and stable isotopic measurements

Plastic cable ties can be utilised in a range of serious criminal activities and a comparison of cable ties, or fragments, may form part of the physical evidence presented to a Court of law. This research assessed the potential value of evidence based on the analysis of plastic cable ties. Twenty packets of black coloured plastic cable ties (nominally 200 mm × 4.8 mm) were purchased in pack sizes ranging from 25 to 100 individual cable ties (Brisbane, Australia, March 2015). Representative samples from each packet were visually examined, compared and tested to determine their physical dimensions, chemical compositions and stable isotopic compositions (δ²H, δ¹³C and δ¹⁵N).All of the individual cable ties from a given packet were found to be indistinguishable with respect to appearance, physical, chemical and isotopic measurements (within-batch variability). Individual cable ties were also found to be isotopically homogeneous with respect to hydrogen, carbon and nitrogen. All of the cable ties analysed were found to have very similar chemical compositions and to be manufactured predominantly from nylon 6,6. The elemental compositions of composite samples, prepared from each packet, were found to be highly variable and, as such, were of very limited value.Cable ties from ten of the twenty packets were uniquely characterised by physical appearance (between-batch variability). Physical measurements such as the width, thickness and tooth-count of the grip section did not provide additional discrimination. Cable ties from nineteen of the twenty packets were uniquely characterised by isotopic composition, based on δ²H and δ¹⁵N measurements. Samples from two packets of Crescent brand cable ties were found to be indistinguishable with respect to all of the tests applied in this study. These two packets were inadvertently purchased from the same retailer and had the same barcode and batch number. It was considered a reasonable assumption that these two packets originated from the same manufacturing batch.The authors reason that a likelihood ratio (that might be presented to a Court of law) can be derived from this type of discrete data based on a calculation of the possible combinations of distinguishable objects (unordered sampling with replacement) in a convenience sample collected from the background population. In this example, a database of 19 distinguishable objects can yield a likelihood ratio as high as 210, with a verbal equivalent of “moderately strong support” for a proposition that two cable ties have the same isotopic composition because they originate from the same batch rather than by random chance.     

Texas Population Substructure and Its Impact on Estimating the Rarity of Y STR Haplotypes from DNA Evidence*

Abstract: Three sampled populations of unrelated males—African American, Caucasian, and Hispanic, all from Texas—were typed for 16 Y short tandem repeat (STR) markers using the AmpFlSTR^® Yfiler^TM kit. These samples also were typed previously for the 13 core CODIS autosomal STR loci. Most of the 16 marker haplotypes (2478 out of 2551 distinct haplotypes) were observed only once in the data sets. Haplotype diversities were 99.88%, 99.89%, and 99.87% for the African American, Caucasian, and Hispanic sample populations, respectively. F_ST values were very small when a haplotype comprised 10–16 markers. This suggests that inclusion of substructure correction is not required. However, haplotypes consisting of fewer loci may require the inclusion of F_ST corrections. The testing of independence of autosomal and Y STRs supports the proposition that the frequencies of autosomal and Y STR profiles can be combined using the product rule.     

Rape Co-occurrence: Do Additional Crimes Affect Victim Reporting and Police Clearance of Rape?

Despite the increased research attention given to rape and violence against women, little is known about rape co-occurrence, or rape incidents that involve another crime. Although previous research has found certain incident characteristics increase the likelihood that a victim reports her rape to police and that the offender is arrested and prosecuted, the relationship between co-occurrence and these responses is unknown. Given this gap in the literature, the main goal of the present research is to provide an initial understanding of rape co-occurrence and its effect on victim reporting and police clearance. To explore these issues, this study uses two national data sources that collect the requisite incident-level information: the National Crime Victimization Survey and the Uniform Crime Reporting Program’s National Incident-Based Reporting System. Few rapes are found to co-occur with other crimes. When rapes do occur with other crimes, though, they are more likely than solo-occurring rapes to involve weapons, strangers, additional injury to the victim, and multiple offenders. Rapes that co-occur also are more likely to be reported to police and cleared by police than rapes that occur with no other crimes.

Hungarian population data of eight X-linked markers in four linkage groups

The X chromosomal STR markers DXS10135 and DXS8378 in linkage group 1, DXS7132 and DXS10074 in linkage group 2, HPRTB and DXS10101 in linkage group 3, and DXS10134 and DXS7423 in linkage group 4 were studied in the Hungarian population. After genotyping unrelated men (219) and women (165), forensic efficiency parameters were calculated. Deviations from Hardy-Weinberg equilibrium could not be detected. There were several microvariant and rare alleles were sequenced: four in locus DXS10135 (alleles 17.1, 18.1, 20.1 and 26.1), one in locus DXS10074 (alleles 11), three in locus DXS10101 (alleles 26, 34.2 and 35) and five in locus DXS10134 (alleles 35.3, 37.2, 38.2, 39.2, 41).     

Validation of Tool Mark Comparisons Obtained Using a Quantitative,Comparative, Statistical Algorithm

Abstract: A statistical analysis and computational algorithm for comparing pairs of tool marks via profilometry data is described. Empirical validation of the method is established through experiments based on tool marks made at selected fixed angles from 50 sequentially manufactured screwdriver tips. Results obtained from three different comparison scenarios are presented and are in agreement with experiential knowledge possessed by practicing examiners. Further comparisons between scores produced by the algorithm and visual assessments of the same tool mark pairs by professional tool mark examiners in a blind study in general show good agreement between the algorithm and human experts. In specific instances where the algorithm had difficulty in assessing a particular comparison pair, results obtained during the collaborative study with professional examiners suggest ways in which algorithm performance may be improved. It is concluded that the addition of contextual information when inputting data into the algorithm should result in better performance.     

Crime Statistics as Constructs: The Case of Swedish Rape Statistics

Using Swedish rape statistics as a focus, this article aims to empirically describe the way in which different factors affect official crime statistics produced at the national level. It is argued that cross-national comparisons of crime levels are extremely hazardous when based on official crime statistics, since the construction rules vary widely. International comparisons of crime levels should as a rule be confined to findings of international victim surveys. The example of rape statistics in Sweden - about three times higher when compared to other countries in the European Sourcebook - is used to explain what factors can influence statistics. Statistical, legal and substansive factors are to be taken into account. The author shows that changes in statistical routines, the legal definition of rape and changes over time all influence the statistics in a substansive way. This article indicates the great extent to which crime statistics are a construct, whose appearance is very sensitive to the rules applied in the process of construction. In order to employ statistics appropriately, a thorough knowledge of the principles guiding this process is therefore essential.     

How International Reputation Matters: Revisiting Alliance Violations in Context

We investigate the role of international reputation in alliance politics by developing a signaling theory linking past alliance violations with the formation of future alliance commitments. In our theory, past violations Are useful signals of future alliance reliability conditional on whether they effectively separate reliable from unreliable alliance partners. It follows that states evaluating potential alliance partners will interpret past violations in their context when deciding to enter a new alliance, attaching less weight to violations in “harder times,” when many states are defaulting on their alliance commitments together, and more weight to violations in “easier times,” when fewer states are defaulting on their alliances. We test our theory and find that states are empirically more likely to form new alliances with states that violated in harder times compared to states that violated in easier times. The results have important implications for how scholars understand and estimate the impact of international reputation.     

The Impact of Discontinuation of the Medical Examiner System: Cases of Drowning in the Bathtub at Home

The incidence of death by drowning greatly varies among different prefectures in Japan, mainly due to climate difference. However, there could be other factors affecting the incidence of deaths besides climate, for example, differences in regional death investigation systems. Here, we aimed to elucidate other such factors affecting the mortality data of drowning in the bathtub, especially the effects of discontinuing the medical examiner system. Police data in Kyoto and ambulatory care information in Yokohama were used. Data on cases of elderly individuals found dying or dead in the bathtub at home in winter 2014–2015 were obtained. The following data were collected for each case: age, gender, presence/absence of ambulatory transport, performance of autopsy, and cause of death. The autopsy and drowning rates in Kyoto were 0%, whereas both values in Yokohama were significantly higher at 93.1% and 89.4%, respectively (the denominator of each of the rates is the total number of elderly (aged 65 or over) individuals found dying or dead in the bathtub at home in each city during each winter). Despite no significant difference of incidence of total bath-related death, the proportion of drowning-related deaths was overwhelmingly higher in Yokohama than in Kyoto. The difference can be attributed to the difference in autopsy rates between the two cities, mainly caused by the presence/absence of a medical examiner system. Therefore, we should pay careful attention to future changes in autopsy/drowning rates in Yokohama, and ascertain whether the change might be continuously influenced by the abolishment of this system.