Application of superimposition-based personal identification using skull computed tomography images

Superimposition has been applied to skulls of unidentified skeletonized corpses as a personal identification method. The current method involves layering of a skull and a facial image of a suspected person and thus requires a real skeletonized skull. In this study, we scanned skulls of skeletonized corpses by computed tomography (CT), reconstructed three-dimensional (3D) images of skulls from the CT images, and superimposed the 3D images with facial images of the corresponding persons taken in their lives. Superimposition using 3D-reconstructed skull images demonstrated, as did superimposition using real skulls, an adequate degree of morphological consistency between the 3D-reconstructed skulls and persons in the facial images. Three-dimensional skull images reconstructed from CT images can be saved as data files and the use of these images in superimposition is effective for personal identification of unidentified bodies.     

An investigation into the accuracy and reliability of skull-photo superimposition in a South African sample

One of the aims of forensic science is to determine the identities of victims of crime. In some cases the investigators may have ideas as to the identities of the victims and in these situations, ante mortem photographs of the victims could be used in order to try and establish identity through skull-photo superimposition. The aim of this study was to evaluate the accuracy of a newly developed digital photographic superimposition technique on a South African sample of cadaver photographs and skulls. Forty facial photographs were selected and for each photo, 10 skulls (including the skull corresponding to the photo) were used for superimposition. The investigator did not know which of the 10 skulls corresponded to the photograph in question. The skulls were scanned 3-dimensionally, using a Cyberware? Model 3030 Colour-3D Scanhead scanner. The photos were also scanned. Superimposition was done in 3D Studio Max and involved a morphological superimposition, whereby a skull is superimposed over the photo and assessed for a morphological match. Superimposition using selected anatomical landmarks was also performed to assess the match. A total of 400 skull-photo superimpositions were carried out using the morphological assessment and another 400 using the anatomical landmarks. In 85% of cases the correct skull was included in the possible matches for a particular photo using morphological assessment. However, in all of these cases, between zero and three other skulls out of 10 possibilities could also match a specific photo. In the landmark based assessment, the correct skull was included in 80% of cases. Once again, however, between one and seven other skulls out of 10 possibilities also matched the photo. This indicates that skull-photo superimposition has limited use in the identification of human skeletal remains, but may be useful as an initial screening tool. Corroborative techniques should also be used in the identification process.     

Computer-assisted skull identification system using video superimposition

This system consists of two main units, namely a video superimposition system and a computer-assisted skull identification system. The video superimposition system is comprised of the following five parts: a skull-positioning box having a monochrome CCD camera, a photo-stand having a color CCD camera, a video image mixing device, a TV monitor and a videotape recorder. The computer-assisted skull identification system is composed of a host computer including our original application software, a film recorder and a color printer. After the determination of the orientation and size of the skull to those of the facial photograph using the video superimposition system, the skull and facial photograph images are digitized and stored within the computer, and then both digitized images are superimposed on the monitor. For the assessment of anatomical consistency between the digitized skull and face, the distance between the landmarks and the thickness of soft tissue of the anthropometrical points are semi-automatically measured on the monitor. The wipe images facilitates the comparison of positional relationships between the digitized skull and face. The software includes the polynomial functions and Fourier harmonic analysis for evaluating the match of the outline such as the forehead and mandibular line in both the digitized images.     

Identification of skulls by video superimposition

A method of matching skulls with photographic portraits or impressions of the face in clay by video superimposition is described. Two different practical cases are presented. The first one deals with the identification of a skull of a six-year-old girl, the second with the identification of the skull of the famous Swiss Pedagogue Johann Heinrich Pestalozzi, who died about 160 years ago. The advantages and versatility of this method are shown; also the setup of the equipment and the working technique.     

Reliability of Craniofacial Superimposition Using Three‐Dimension Skull Model

Craniofacial superimposition is a technique potentially useful for the identification of unidentified human remains if a photo of the missing person is available. We have tested the reliability of the 2D‐3D computer‐aided nonautomatic superimposition techniques. Three‐dimension laser scans of five skulls and ten photographs were overlaid with an imaging software. The resulting superimpositions were evaluated using three methods: craniofacial landmarks, morphological features, and a combination of the two. A 3D model of each skull without its mandible was tested for superimposition; we also evaluated whether separating skulls by sex would increase correct identifications. Results show that the landmark method employing the entire skull is the more reliable one (5/5 correct identifications, 40% false positives [FP]), regardless of sex. However, the persistence of a high percentage of FP in all the methods evaluated indicates that these methods are unreliable for positive identification although the landmark‐only method could be useful for exclusion.     

Skull-photo superimposition and border deaths: identification through exclusion and the failure to exclude

We report on the application of video skull-photo superimposition as an identification method in a case from Ajo, Arizona in which five individuals died after crossing into southern Arizona from Mexico. Initial analyses at the Pima County Forensic Science Center in Tucson, Arizona determined that the disarticulated skeletal remains represented two adult Hispanic males and three adult Hispanic females. Based on biological profiles, both the males and one of the females were tentatively identified and assigned names. The other two females were too similar in age and height, making skeletal separation and identification difficult. As a result, the Michigan State University Forensic Anthropology Laboratory assisted in the identification efforts by performing video skull-photo superimposition on the two unknown females. The skulls were compared to a photograph reported to be one of the missing females. By evaluating facial proportionality and by comparing a number of morphological features of the face and skulls, one skull was excluded as a possible match and one skull was not excluded as a match to the antemortem photo. Because this case was presumed to be a closed disaster, the exclusion of one skull and the failure to exclude the other represented circumstantial identifications.     

A novel skull registration based on global and local deformations for craniofacial reconstruction

Craniofacial reconstruction is important in forensic identification. It aims to estimate a facial appearance for human skeletal remains using the relationship between the soft tissue and the underlying bone structure. Various computerized methods have been developed in recent decades. An effective way is to deform a reference skull to the discovered skull, and then apply the same deformation to the skin associated with the reference skull to provide an approximate face for the discovered skull. For this method, the better the two skulls match each other, the more face-like the reconstructed skin surface will be. In this paper, we present a novel skull registration method that can match the two skulls closely, so as to improve the accuracy of the reconstruction. It combines both global and local deformations. A generic thin-plate spline (TPS)-based deformation, which is global, is applied first to roughly align the two skulls based on two groups of manually defined landmarks. Afterwards, the two skulls are largely matched, except some regions, on which some new landmarks are automatically marked. A compact support radial basis functions (CSRBF)-based deformation, which is local, will then be performed on these regions to adjust the initial alignment of the two skulls. Such adjustment can be repeatedly implemented until the two skulls have optimal alignment. In addition, all the skulls and face involved in the registration are represented by their single outer surfaces to facilitate the reconstruction procedure. The experiments demonstrate that our method can create a plausible face even when the reference skull is very different from the discovered skull. As a result, we can make full use of our database to provide multiple estimates for a principle components analysis (PCA) for the final reconstruction.     

The colour of the human skull

The colour of the human skull was determined from 124 fresh skull samples using the tristimulus colour measurement system "Micro Color" and listed as The Commission Internationale de l'Eclairage (CIE) L*a*b*-values. The skulls were found to be relatively light (L*=72.5), nearly colourless on the a*-axis (a*=-7.4), and slightly yellow (b*=16.4). No difference was found between the colours of the outer and the inner surfaces of the skulls. Including a small number (n=8) of skulls from diabetic patients in the study, we detected no colour difference between the samples from diabetics and non-diabetics. However, a hitherto unknown correlation between the subjects' age and the yellowness (b*-value) of the skull could be demonstrated.     

Video superimposition at the C.A. Pound Laboratory 1987 to 1992.

William R. Maples practiced many aspects of human identification using simple and relatively inexpensive video superimposition equipment. Identification of skulls by comparison to known photographs was a primary concern. Clear, smiling photographs revealing the spatial relationships of the teeth to one another led to uncomplicated positive identifications. However, without benefit of dentition, how accurate was an identification based on the alignment of soft tissues with the underlying skull? Most importantly, how often would a false positive result when anterior dentition were not available? A study conducted by this author and Dr. Maples used three human heads and 98 profile and full-face photographs. A 0.6% incidence of false match resulted when both views of the face were used. Lateral view and frontal view superimpositions were identified incorrectly in 9.6% and 8.5% of the sample respectively. As a result, multiple photographs from varying angles were requested for superimposition identity cases. Additional applications in laboratory case work were developed for the equipment. Light boxes under the television cameras allowed radiographic comparisons. Video taped comparisons of antemortem and postmortem radiographs were shown to medical examiners and families as proof of identification. Dr. Maples and this author were also involved in several cases in which photographs taken by a surveillance or ATM camera were compared to court ordered photographs of an alleged perpetrator. One case, which went to trial, led to the conviction of a habitual criminal under Florida statute. This individual had a condition known as Stahl's ear, a deformation of the cartilaginous structure. The ear was seen clearly in many of the ATM camera photographs and was aligned easily with the known photographic sample.     

Evaluation of pediatric skull fracture imaging techniques

Radiologic imaging is crucial in the diagnosis of skull fracture, but there is some doubt as to whether different imaging modalities can accurately identify fractures present on a human skull. While studies have been performed to evaluate the efficacy of radiologic imaging at other anatomical locations, there have been no systematic studies comparing various CT techniques, including high resolution imaging with and without 3D reconstructions to conventional radiologic imaging in children, we investigated which imaging modalities: high-resolution CT scan with 3D projections, clinical-resolution CT scans or X-rays, best showed fracture occurrence in a pediatric human cadaver skull by having an expert pediatric radiologist examine radiologic images from fractured skulls. The skulls used were taken from pediatric cadavers ranging in age from 5 months to 16 years. We evaluated the sensitivity and specificity for the imaging modalities using dissection findings as the gold standard. We found that high-resolution CT scans with 3D projections and conventional CT provided the most accurate fracture diagnosis (single-fracture sensitivity of 71%) followed by X-rays (single-fracture sensitivity of 63%). Linear fractures outsider the region of the sutures were more identifiable than diastatic fractures, though the incidence of false positives was greater for linear fractures. In the two cases where multiple fractures were present on the same anatomical skull location, the radiologist was less likely to identify the presence of additional fractures than a single fracture. Overall, the high-resolution and clinical-resolution CT scans had the similar accuracy for detecting skull fractures while the use of the X-ray was both less accurate and had a lower specificity.     

Identification of unknown dead bodies by X-ray image comparison of the skull using the X-ray simulation program FoXSIS

The aim of the study was to improve the objectivity of X-ray image comparison for the identification of unknown dead individuals. CT-data were collected for 30 macerated skulls. An already presented computer program which uses CT data to establish virtual X-ray images was used to obtain X-rays with different beam angulations simulating rotation, dorsal flexion, and ventral flexion. Specific parameters were measured on the simulated images. The frontal sinus reveals the highest variability not only between the individual skulls but also within an individual skull in different positions. The most consistent parameters with respect to different positions were the skull breadth, the biorbital breadth and the bizygomatic breadth. In a blind study, three out of 24 skulls could clearly be identified just by measured distances although the positions were different and unknown to the investigator. The dimensions of the frontal sinus do not correlate with the other skull parameters (analysis of covariance). Based on the presented results, we propose a method that will calculate the probability of identity. The presented results demonstrate that the comparison of X-ray images can be undertaken in an objective way by quantifying the probability of identity even when the comparative images were made under different conditions.     

Identification of skull from its suture pattern

The examination of 320 skulls collected at random revealed that the ectocranial suture patterns in them are highly individualistic and that no two skulls can ever have an identical pattern. The possibility of these suture patterns being recorded incidentally in routine diagnostic skull radiographs was verified by examining the skull skiagrams preserved in radiology departments. A positive method of identification of the skull is suggested by the comparison of radiographic with visible skull suture pattern.     

Application of 3-D computer graphics for facial reconstruction and comparison with sculpting techniques

Facial reconstruction has until now been carried out by the sculpting technique. This method involves building a face with clay or other suitable material on to a skull or its cast, taking into account appropriate facial thickness measurements together with information provided by anthropologists such as approximate age, sex, race and other individual idiosyncrasies. A method for facial reconstruction is presented using 3-D computer graphics and is compared with the manual technique. The computer method involves initially digitising a skull using a laser scanner and video camera interfaced to a computer. A face, from a data bank which has previously digitised facial surfaces, is then placed over the skull in the form of a mask and the skin thickness is altered to conform with the underlying skull. The advantage of the computer method is its speed and flexibility. We have shown that the computer method for reconstructing a face is feasible and furthermore has the advantage over the manual technique of speed and flexibility. Nevertheless, the technique is far from perfect. Further facial thickness data needs collecting and the method requires evaluation using both known control skulls and later unknown remains.     

Computer analysis of face and skull size by "quantitative verbal portrait" method

The aim of this study was to develop a "quantitative verbal portrait" method on the basis of universal measured signs of the face and skull. The database includes 90 cases with expert evaluation of photocompatibility with proven identity. Four groups of signs were investigated: DX and DY--the width and height between accurately fixed concrete craniometrical (facial) points and the so-called RX and RY indices--the ratio between distances within the framework of the same direction. The proposed scheme of evaluation helps compare the photograph of a live human and the skull. For evaluating the degree of identity, one should have a summary characterization of all selected signs for the skull and compare it with the sum on the photograph; sometimes it is possible to rule out the identity of the photograph and the skull by the absolute size, e.g., a very large skull cannot belong to a human with a very little face. The score for each group of signs is used for analysis of the information for detecting the similarities. Accumulation and comparative analysis of two information flows are possible: database on portraits of lost subjects and database on graphic images of the skulls of unidentified corpses.     

面部整容术对颅像重合的影响分析

颅像重合法对身源不明的颅骨个体识别已在国内开展二十余年,其依据是对送检的失踪人照片面部软组织与颅骨之间标志点、线的对应量度关系做出是否同一人的认定。经多年观察总结面部整容术的方法、部位及形态与颅像重合标志点、线量度间的影响问题,对于人群中是否有部分人是面部整容术后的面像判断,提出相关专业人员的鉴定分析方法。     

Remote control skull positioning device for superimposition studies.

The success of the superimposition technique requires positioning the skull in the same posture of the face as seen in the given photograph. A scientific method for positioning the skull has already been proposed by Sekharan. This paper deals with the simple remote control tilt and rotatory device developed in the Forensic Sciences Department, Madras. A pan and tilt arrangement usually utilized in surveillance cameras and two a.c. servomotors, one to tilt the pan and the other to rotate the pan are used.     

Fourier analysis of the forehead shape of skull and sex determination by use of computer

The forehead shape of the skull was quantified with the Fourier analysis method by using 100 male and 100 female radiographic lateral views of the skull, and sex difference in the forehead shape was studied. Furthermore to predict the sex of cranial specimens, an automated sexing computer system based on the quantification was created. The effectiveness of the system was evaluated by checking 56 male and 56 female specimens of skulls. This system was proved to discriminate male and female skulls from forehead shapes with 85% accuracy.     

Development of equipment for the standardization of skull photographs in personal identifications by photographic superimposition

The technique of photographic superimposition of postmortem specimens (dried skull or head) positioned identically to the orientation in an antemortem smiling photograph is now a recognized method for personal identification of human remains. Previous methods used to produce the postmortem photographs were problematic as orientation of the specimen could not be easily adjusted and positions were not reproducible. The objective of this paper is to describe the design and method of use of purpose-constructed equipment intended to alleviate these problems. The equipment comprises a skull-holding jig based conceptually on the Royal Berkshire Hospital halo frame. This is mounted on a pan-and-tilt device, incorporating calibrated measurement scales, enabling independent movements in each of the Cartesian coordinates. A camera is attached to an adjustable mount running on twin parallel rails allowing the camera-to-specimen distance to be varied. The equipment has proven to be straightforward in use and offers considerable advantages over previously described methods for producing postmortem photographs.     

A method of orientation of skull and camera for use in forensic photographic investigation

The ability to obtain accurate superimposition of the image of the teeth from ante- and post-mortem dentitions is a prerequisite of photographic superimposition. A prototype skull and camera holder is described that enables this to be achieved quickly and simply. The position of the skull relative to the attitude of the face in the photograph can then be documented and hence reproduced as required.     

Determination of race and sex of the human skull by discriminant function analysis of linear and angular dimensions

The race and sex of the human skull can be determined by craniometry. In this paper we suggest that a large number of craniometric measurements does not necessarily give the best possible discrimination for race and test the performance of subsets of variables drawn from various skull regions, or extracted mathematically on the basis of their discriminatory power. We also suggest that the best discriminators for race are not necessarily the best for sex, and that skulls of unknown provenance are best tested first for race and then for sex, using different variables for each purpose.