Comparative Assessment of a Novel Photo‐Anthropometric Landmark‐Positioning Approach for the Analysis of Facial Structures on Two‐Dimensional Images

Positioning landmarks in facial photo‐anthropometry (FPA) applications remains today a highly variable procedure, as traditional cephalometric definitions are used as guidelines. Herein, a novel landmark‐positioning approach, specifically adapted for FPA applications, is introduced and, in particular, assessed against the conventional cephalometric definitions for the analysis of 16 landmarks on ten frontal images by two groups of examiners (with and without professional knowledge of anatomy). Results showed that positioning reproducibility was significantly better using the novel method. Indeed, in contrast to the classic approach, very low landmark dispersions were observed for both groups of examiners, which were usually below the strictest clinical standards (i.e., 0.575 mm). Furthermore, the comparison between the two groups of examiners highlighted higher dispersion consistencies, which supported a higher robustness. Thus, the use of an adapted landmark‐positioning approach proved to be highly advantageous in FPA analysis and future work in this field should consider adopting similar methodologies.     

Investigation into the use of photoanthropometry in facial image comparison

Photoanthropometry is a metric based facial image comparison technique. Measurements of the face are taken from an image using predetermined facial landmarks. Measurements are then converted to proportionality indices (PIs) and compared to PIs from another facial image. Photoanthropometry has been presented as a facial image comparison technique in UK courts for over 15 years. It is generally accepted that extrinsic factors (e.g. orientation of the head, camera angle and distance from the camera) can cause discrepancies in anthropometric measurements of the face from photographs. However there has been limited empirical research into quantifying the influence of such variables. The aim of this study was to determine the reliability of photoanthropometric measurements between different images of the same individual taken with different angulations of the camera. The study examined the facial measurements of 25 individuals from high resolution photographs, taken at different horizontal and vertical camera angles in a controlled environment. Results show that the degree of variability in facial measurements of the same individual due to variations in camera angle can be as great as the variability of facial measurements between different individuals. Results suggest that photoanthropometric facial comparison, as it is currently practiced, is unsuitable for elimination purposes. Preliminary investigations into the effects of distance from camera and image resolution in poor quality images suggest that such images are not an accurate representation of an individuals face, however further work is required.     

The Effect of Image Quality and Forensic Expertise in Facial Image Comparisons

Images of perpetrators in surveillance video footage are often used as evidence in court. In this study, identification accuracy was compared for forensic experts and untrained persons in facial image comparisons as well as the impact of image quality. Participants viewed thirty image pairs and were asked to rate the level of support garnered from their observations for concluding whether or not the two images showed the same person. Forensic experts reached their conclusions with significantly fewer errors than did untrained participants. They were also better than novices at determining when two high‐quality images depicted the same person. Notably, lower image quality led to more careful conclusions by experts, but not for untrained participants. In summary, the untrained participants had more false negatives and false positives than experts, which in the latter case could lead to a higher risk of an innocent person being convicted for an untrained witness.     

An Assessment of How Facial Mimicry Can Change Facial Morphology: Implications for Identification

The assessment of facial mimicry is important in forensic anthropology; in addition, the application of modern 3D image acquisition systems may help for the analysis of facial surfaces. This study aimed at exposing a novel method for comparing 3D profiles in different facial expressions. Ten male adults, aged between 30 and 40 years, underwent acquisitions by stereophotogrammetry (VECTRA‐3D ^® ) with different expressions (neutral, happy, sad, angry, surprised). The acquisition of each individual was then superimposed on the neutral one according to nine landmarks, and the root mean square (RMS) value between the two expressions was calculated. The highest difference in comparison with the neutral standard was shown by the happy expression (RMS 4.11 mm), followed by the surprised (RMS 2.74 mm), sad (RMS 1.3 mm), and angry ones (RMS 1.21 mm). This pilot study shows that the 3D–3D superimposition may provide reliable results concerning facial alteration due to mimicry.     

Individual identification of disguised faces by morphometrical matching

The reliability of a morphometrical matching method for identifying disguised faces was examined experimentally using a computer-assisted facial image identification system. The 2D right oblique facial images of three target persons disguised with sunglasses, cap and gauze mask were each compared with each of the 3D facial images of 100 subjects, yielding 900 face-to-face superimpositions. The average perpendicular distance between the facial outlines and the average point-to-point distance of the corresponding landmarks in the 2D image of the disguised face and the 3D facial image, were calculated. As a matching criterion, the sum of the values of the average perpendicular difference of the facial outlines and the average point-to-point difference between the corresponding landmarks was used (abbreviation: average difference).The range of the average difference was 2.3-2.8mm for the same person (a match) and 4.0-14.6mm for different (non-matching) people, respectively. The ranges for matching and non-matching faces did not overlap. Even the 3D facial images of the non-matching person showing the closest value of average difference to the average difference for the matching person could be excluded easily. It was concluded that the morphometrical matching method can reliably identify disguised faces and the results produced by this method could be easily understandable by a court of law.     

Development and Validation of a Technique for Casting Anatomical Features and Toolmarks

Time may elapse between examination of marks inflicted on the body and comparison with a potential weapon. Two‐dimensional photographs may be inadequate for effective comparison of a three‐dimensional mark with a putative instrument. Taking a cast and producing a positive image results in a lasting three‐dimensional record. This project aimed to develop and demonstrate the accuracy of an easy technique for production of long‐lasting positive images (using plaster of Paris and dental alginate). Casts of facial features of embalmed cadavers were used to produce a positive image of the face (death mask). Measurements of distances between facial anatomical landmarks were compared with measurements of distances between the same landmarks on the death masks to assess accuracy of reproduction. There were no significant differences between cadaver and death mask in 6 of 9 measurements, indicating this technique has high accuracy with less mobile facial features, but produces deformation of pliable features.     

An Exploration of Sample Representativeness in Anthropometric Facial Comparison*

Abstract: Faces are assumed to be unique, but their use in court has remained problematic as no method of comparison with known error rates has been accepted by the scientific community. Rather than relying on the assumed uniqueness of facial features, previous research has been directed at estimations of face shape frequency. Here, the influence of age, sex, and ancestry on variation was investigated. Statistical shape analysis was used to examine the necessity for sub‐divisions in forensic comparisons, using a large sample of facial images on which 30 anthropometric landmark points had been placed in 3D. Results showed a clear pattern of separation of the sexes in all age groups, and in different age groups in men. It was concluded that sub‐division of databases by sex will be necessary in forensic comparisons. Sub‐division by age may be necessary in men (although not necessarily in women), and may be necessary by ancestry.     

Three-Dimensional Prediction of the Nose for Facial Approximation in a Thai Population

Most of the previous studies about nose prediction were concentrated only some landmarks of the nose. This study aimed to generate prediction equations for ten landmarks of the nose in the midline and alar regions for forensic facial approximation. The six midline landmarks were the sellion, nasion–pronasale posterior, nasion–pronasale anterior, pronasale, nasal drop, and subnasale. The four landmarks of the alar region were the alare, superior alar groove, posterior alar groove, and inferior alar groove. We used the skull landmarks in the nasal, zygomatic, and maxillary bone to predict the landmarks of the nose. Cone-beam computed tomography scans of 108 Thai subjects with normal BMI and age ranging from 21.0 to 50.9 years were obtained in a sitting position. The data were converted into three-dimensional (3-D) images of the skull and face. The Cartesian coordinates of the landmarks of the skull and nose were used to formulate the multiple regression equations. The formulated equations were tested in 24 new subjects. The mean differences in the predicted midline landmarks varied between −0.4 mm and 0.5 mm, whereas those for bilateral landmarks varied between −1.0 mm and 1.4 mm. In conclusion, the prediction equations formulated here will be beneficial for facial approximation of the nose in a Thai population.     

A new technique for three-dimensional ultrasound scanning of facial tissues

We report the development of an ultrasonic facial scanning technique that allows for the visualization of continuous contours without deforming surface tissues. Adhesive markers are placed on the face to enable measurement of facial tissue thicknesses at specific landmarks. The subject immerses the face in a clear plastic box filled with water for about 20 seconds while the researcher moves the transducer along the bottom of the box, guiding transducer movement by watching the facial image in a mirror placed below. 3D Echotech software (1) builds the images from sequentially acquired 2D frames. Reliability of repeat measurements at landmarks is good, and individual tissues (skin, subcutaneous, muscle) can be distinguished. The method is simple, reliable, less expensive and less time consuming than alternatives such as magnetic resonance imaging (MRI). It is applicable in both research and clinical contexts.     

Accuracy of facial soft tissue thickness measurements in personal computer-based multiplanar reconstructed computed tomographic images

The purpose of this study was to determine the precision and accuracy of facial soft tissue measurement using personal computer (PC)-based multiplanar reconstructed (MPR) computed tomography (CT) images and to evaluate the effect of the various CT scanning protocols on the facial soft tissue thickness measurement. Thirteen different CT imaging protocols were used to image a cadaver head. MPR reformations and three-dimensional (3D) reconstructions viewed on a laptop PC were used to make measurements at six specific sites on each set of images. These measurements were compared to physical measurements at the same sites. Increasing the slice thickness resulted in decreased image quality. Within the same slice thickness, increasing the pitch ratio in the spiral mode, resulted in decreasing image quality. The image quality of conventional CT scanning was relatively poorer than that of the spiral CT scanning. However, the mean deviation from the physical measurement was within 0.43 mm in every instance. This mean deviation was quite small and clinically acceptable for measuring the soft tissue thickness of the facial area. PC-based MPR CT images of the face using routine scanning CT protocols can be used to accurately measure soft tissue thickness in the facial region. However, for more fine and accurate data collection, scanning protocols with slice thicknesses less than 5mm, and a spiral/helical mode pitch less than 2:1 are recommended.     

Effect of Head Position on Facial Soft Tissue Depth Measurements Obtained Using Computed Tomography

Facial soft tissue depth (FSTD) studies employing clinical computed tomography (CT) data frequently rely on depth measurements from raw 2D orthoslices. However, the position of each patient's head was not standardized in this method, potentially decreasing measurement reliability and accuracy. This study measured FSTDs along the original orthoslice plane and compared these measurements to those standardized by the Frankfurt horizontal (FH). Subadult cranial CT scans (n = 115) were used to measure FSTDs at 18 landmarks. Significant differences were observed between the methods at eight of these landmarks (p < 0.05), demonstrating that high‐quality data are not generated simply by employing modern imaging modalities such as CT. Proper technique is crucial to useful results, and maintaining control over head position during FSTD data collection is important. This is easily and most readily achieved in CT techniques by rotating the head to the FH plane after constructing a 3D rendering of the data.     

辽宁汉族青年女性面部不对称性的分析

目的研究辽宁汉族青年女性面部的不对称性,为面部识别和颅面复原提供数据。方法随机选择100例正常青年女性,采用MRI摄片,应用VG Studio 2.2MAX软件测量面部的标志点,测量后的右、左侧面部坐标进行欧几里德几何距离矩阵分析（EDMA）,最后使用Geomagic Wrap 12软件对左侧面部三维图像进行镜像合成,生成完全对称的镜像面部并与真实面部进行比较。结果 EDMA分析显示,右、左侧面部有显著形态学差异,bootstrap检验T=1.402,P=0.001,形状差异矩阵（FDM）比值（右侧比左侧）在0.95-1.05的有224个占85%,FDM比值小于0.95和大于1.05的部分有40个占15%,40个不对称比值中有15个小于0.95占37.5%,25个比值大于1.05占62.5%。Geomagic Wrap 12分析结果显示镜像合成的面部与真实面部图像有明显差异。结论辽宁汉族青年女性面部不对称,不对称性为15%,右侧面部比左侧面部不对称性影响大。     

Forensic Facial Comparison: Issues of Admissibility in the Development of Novel Analytical Technique

Much contemporary debate in forensic science concerns validity and admissibility of scientific evidence in court. In this paper, three current approaches to facial identification—image superimposition, photogrammetry, and morphological analysis—are considered with regard to criteria for scientific evidence in the United States, and England, and Wales. The aim of the paper is to assess the extent to which facial image comparison meets criteria of admissibility in these jurisdictions. The method used is a comparative evaluation of the methods of facial image comparison and their underlying premises against the range of admissibility criteria reported in court rulings and relevant judicial and scientific inquiries in the United States and the United Kingdom. While the techniques of facial image comparison are generally accepted within their practitioner communities, they are not tested, and their error rates are unknown. On that basis, the methods of facial image comparison would appear not to meet the anticipated standards. They are, nevertheless, admitted in court in the United States, and England, and Wales. This paper concludes that further research in science and law will be necessary to more definitively establish admissibility of facial image comparison evidence, as it will for other nascent and novel methods that are potentially influential in court proceedings.     

Facial Soft Tissue Thickness Database for Craniofacial Reconstruction in Korean Adults

Abstract: One hundred Korean adults (50 men, 50 women) were scanned in the upright position using a cone‐beam CT (CBCT) scanner. The soft tissue (ST) thicknesses were measured at 31 landmarks, 10 midline and 21 bilateral landmark sites, and the means and standard deviations were obtained for male and female subjects. While 18 of 31 landmarks showed sex differences, the majority showed higher values for male subjects with the exception of a few landmark sites corresponding to the zygoma area, which showed smaller values in men than in women. The mandibular area showed greater differences between the right and left sides. Overall, the ST thickness measurements obtained in this study can be used as a database for the forensic craniofacial reconstruction of Korean adult faces.     

图像降噪和增强对人脸识别系统识别性能的影响

目的研究图像降噪和图像增强方法对人脸识别系统识别性能的影响,以期为人脸识别系统应用过程中的图像处理方法选取提供理论指导和技术方案。方法收集33起人像鉴定领域实际案例中的人脸图像素材,研究以高斯滤波和小波变换为代表的图像降噪技术以及具有边缘保持和小波变换特性的单帧图像超分辨率增强技术对人脸识别系统识别性能的影响,并对不同图像处理方法对人脸识别性能的影响进行量化比较分析。结果本文研究的图像降噪技术均显著提高了人脸识别系统的识别准确性,而图像增强技术虽然提高了人脸图像显示效果,但对人脸识别系统的识别性能无正向促进作用。此外,高斯模糊图像处理的图像降噪方法虽然简单,但与本文研究的其他方法比较,其在人脸识别系统识别性能改善方面效果最显著。结论人脸图像质量对人脸识别系统的识别性能具有显著影响,可以通过图像处理技术改善人脸图像质量进而提高人脸识别系统的识别准确性。其中,图像降噪处理可以显著提高人脸识别系统的识别性能,且比图像增强技术更适合于实际人像鉴定应用中的人脸识别系统识别性能增强。