A comparison of animal jaws and bite mark patterns

The purpose of this study was to compare the jaw shapes and bite mark patterns of wild and domestic animals to assist investigators in their analysis of animal bite marks. The analyses were made on 12 species in the Order Carnivora housed in the Mammalian Collection at the Field Museum of Natural History in Chicago, Illinois. In addition to metric analysis, one skull from each species was photographed as a representative sample with an ABFO No. 2 scale in place. Bite patterns of the maxillary and mandibular dentition were documented using foamed polystyrene exemplars, which were also photographed. A total of 486 specimens were examined to analyze the jaw and bite mark patterns. A modified technique for measuring intercanine distances was developed to more accurately reflect the characteristics seen in animal bite marks. In it, three separate areas were measured on the canines, rather than just the cusp tip. This was to maximize the amount of information acquired from each skull, specifically to accommodate variances in the depth of bite injuries.     

An integrated technique for the analysis of skin bite marks

The high number of murder, rape, and child abuse cases in South Africa has led to increased numbers of bite mark cases being heard in high courts. Objective analysis to match perpetrators to bite marks at crime scenes must be able to withstand vigorous cross-examination to be of value in conviction of perpetrators. An analysis technique is described in four stages, namely determination of the mark to be a human bite mark, pattern association analysis, metric analysis and comparison with the population data, and illustrated by a real case study. New and accepted techniques are combined to determine the likelihood ratio of guilt expressed as one of a range of conclusions described in the paper. Each stage of the analysis adds to the confirmation (or rejection) of concordance between the dental features present on the victim and the dentition of the suspect. The results illustrate identification to a high degree of certainty.     

Effectiveness of comparison overlays generated with DentalPrint software in bite mark analysis

Validation studies of the new DentalPrint software were carried out with experimental bite marks in pigskin. The bite marks were digitally photographed according to the ABFO guidelines for evidence collection. Dental casts used in the experiment were scanned in 3D and 2D, and comparison overlays were generated using DentalPrint and Adobe Photoshop software, respectively. Digitized photographs of the experimental bite marks and the biting edges obtained in the overlays were compared by two different examiners to analyze the impact of training and experience with the two methods. Receiver operating characteristic (ROC) analysis, sensitivity, specificity, and 95% confidence intervals for each cutoff point were calculated. The expert examiner using DentalPrint obtained the best results, with an area under the ROC curve of 0.76 (SE=0.057; CI at 95%=0.652-0.876). Fairly high specificity values were found for DentalPrint, and the best results were obtained for the cutoff value that discriminated between the examiner's response "biter" and the rest of the possible (specificity 97.9%, CI at 95%=93.2%-99.6%). Therefore, the results presented here indicate that DentalPrint is a useful, accurate tool for forensic purposes, although further research on the comparison process is needed to enhance the validity of bite mark analysis.     

咬痕个体识别的比对方法

目的 建立一个牙模数据库,为通过牙齿、咬痕进行个人识别的研究及其在法医实践中的应用提供一种新方法。方法 经过对400例牙模进行分析、计算,将牙齿的形状、排列转换成数字型(X,Y)坐标,通过计算出每颗牙关键点与坐标原点的相对位置,在DOS系统下运用Borland C++5.0语言编写程序,快速地计算出牙齿和牙弓的特征。结果 能对牙模进行自动识别,达到排除与认定。其比对精度长度为1.3mm,角度3°;可取的最少牙点位数目为12～14较为合理,大致需要5～7个完整的牙痕。结论 该方法是研究咬痕与牙模比对的基础。     

A framework for estimating probability of a match in forensic bite mark identification

In forensic dentistry, a human expert typically does the comparison and identification based on bite marks. Unlike DNA analysis, however, there is no quantitative basis with which to assign a probability for this given match. This paper proposes a framework for empirically estimating the probability of such a bite mark match and reports on initial experimental results. The methodology involved collection of dental population data (3D dental casts and bite mark images), image analysis for quantitatively measuring the degree of match (based on chamfer distance), and performing a logistic regression analysis using the collected population data to estimate the probability of match from the calculated degree of match. The model correctly predicted 35 of the 42 matches and 585 of the 588 mismatches. The method also has potential for use in other forensic applications in which the assignment of quantitative probabilities is important.     

A Morphological and Morphometric Study of Bite Marks Caused by Mice (Mus Musculus) on Different Baits for Forensic Purposes

In animal bites, the dental attributes can be fundamental in identifying the marks made by various species on different matrices. Although rodent bite marks have been studied in the context of postmortem interference, little research has used different baits to analyze these marks linking not only specific behavior patterns but also the possibility of structural damage. Twenty mice (Mus musculus) were exposed to different baits to study their bite marks in a controlled model. The known pattern of parallel and multiple grooves has been seen in all baits, but polyvinyl chloride and fiber‐optic cable were significantly different between each other and the other baits. Some baits showed patterns of anchorage of the upper incisors and space between the lower incisors when gnawing. This technical note represents a novel model of analysis where veterinarians and/or dentists may be asked to give an opinion on alleged animal bite marks.     

多层螺旋CT及后处理技术在眼眶骨折法医鉴定中的应用

目的探讨MSCT及后处理技术在眼眶骨折法医鉴定中的应用价值。方法采用MSCT对98例法医鉴定者进行薄层扫描并行多平面重建(MPR)和表面遮盖成像(SSD)处理。比较MSCT与常规CT诊断结果。结果爆裂骨折51例(52.04%),直接骨折32例(32.65%),复合骨折11例(11.22%),未见骨折4(4.09%)例。常规CT漏、误诊32例(32.65%)。98例患者经MSCT检查明确诊断。二者诊断结果存在显著统计学差异(χ2=66.00,P<0.001)。结论MSCT及后处理技术在眼眶骨折法医鉴定中具有较高的实用价值。     

A simple technique for imaging the human skeleton using a flatbed scanner

A simple technique for imaging the human skeleton with a flatbed scanner is presented using the auricular surface of the ilium as an example. A flatbed scanner with resolution capabilities of 600 dpi or greater allows for images of human bones. The auricular surface of the ilium was selected to demonstrate this technique as it is a fairly three-dimensional area that can be difficult to record photographically. Fifty left ilia of various ages at death from the Athens Collection were selected from which three observers (SCF, CE, and IM) scored the morphology of the auricular surface using a well-established aging method. Observations were taken of the dry bone, of digital photographs of the bone, and of scanned images of the bone, and in that sequence. Results indicate that scores of scanned images are equivalent or better than digital images of the same ilia. This technique allows for sharing data electronically with ease.     

A Novel Method for the Photographic Recovery of Fingermark Impressions from Ammunition Cases Using Digital Imaging

The photographic preservation of fingermark impression evidence found on ammunition cases remains problematic due to the cylindrical shape of the deposition substrate preventing complete capture of the impression in a single image. A novel method was developed for the photographic recovery of fingermarks from curved surfaces using digital imaging. The process involves the digital construction of a complete impression image made from several different images captured from multiple camera perspectives. Fingermark impressions deposited onto 9‐mm and 0.22‐caliber brass cartridge cases and a plastic 12‐gauge shotgun shell were tested using various image parameters, including digital stitching method, number of images per 360° rotation of shell, image cropping, and overlap. The results suggest that this method may be successfully used to recover fingermark impression evidence from the surfaces of ammunition cases or other similar cylindrical surfaces.     

Identification Method for Digital Image Forgery and Filtering Region through Interpolation

Because of the rapidly increasing use of digital composite images, recent studies have identified digital forgery and filtering regions. This research has shown that interpolation, which is used to edit digital images, is an effective way to analyze digital images for composite regions. Interpolation is widely used to adjust the size of the image of a composite target, making the composite image seem natural by rotating or deforming. As a result, many algorithms have been developed to identify composite regions by detecting a trace of interpolation. However, many limitations have been found in detection maps developed to identify composite regions. In this study, we analyze the pixel patterns of noninterpolation and interpolation regions. We propose a detection map algorithm to separate the two regions. To identify composite regions, we have developed an improved algorithm using minimum filer, Laplacian operation and maximum filters. Finally, filtering regions that used the interpolation operation are analyzed using the proposed algorithm.     

A New Anti‐forensic Scheme—Hiding the Single JPEG Compression Trace for Digital Image

To prevent image forgeries, a number of forensic techniques for digital image have been developed that can detect an image's origin, trace its processing history, and can also locate the position of tampering. Especially, the statistical footprint left by JPEG compression operation can be a valuable source of information for the forensic analyst, and some image forensic algorithm have been raised based on the image statistics in the DCT domain. Recently, it has been shown that footprints can be removed by adding a suitable anti‐forensic dithering signal to the image in the DCT domain, this results in invalid for some image forensic algorithms. In this paper, a novel anti‐forensic algorithm is proposed, which is capable of concealing the quantization artifacts that left in the single JPEG compressed image. In the scheme, a chaos‐based dither is added to an image's DCT coefficients to remove such artifacts. Effectiveness of both the scheme and the loss of image quality are evaluated through the experiments. The simulation results show that the proposed anti‐forensic scheme can verify the reliability of the JPEG forensic tools.     

Robust Shoeprint Retrieval Method Based on Local‐to‐Global Feature Matching for Real Crime Scenes

In this study, an automatic and robust crime scene shoeprint retrieval method is proposed. As most shoeprints left at crime scenes are randomly partial and noisy, crime scene shoeprint retrieval is a challenging task. To handle partial, noisy shoeprint images, we employ denoising deep belief network (DBN) to extract local features and use spatial pyramid matching (SPM) to obtain a local‐to‐global matching score. In this study, 536 query shoeprint images from crime scenes and a large scale database containing 34,768 shoeprint images are used to evaluate the retrieval performance. Experimental results show that the proposed method outperforms other state‐of‐the‐art methods in terms of retrieval accuracy, feature dimension, and retrieval speed. The proposed method achieves a cumulative match score (CMS) of 65.67% at top 10 which is 5.60% higher than the second best performing method.