Critical Analysis On Skull Superimposition Techniques

Contents

Abstract

The technique of skull superimposition from photographs is one of the most emerging techniques in forensic anthropology. By using this method, the deceased one or the unknown can be discovered. This is possible by superimposing the photograph of the individual suspected of belonging to the unidentified skeletal remains over an X-ray of the unidentified skull. This paper describes about how facial reconstruction is done by superimposing photographs and the advancements made so far and also try to define in what all ways does it aids the parameters of forensic anthropology. This article also discusses the various methods, advancements, types of superimpositions and also elaborates on the negatives and affirmatives on the same. The aim of this article is to expand on the attempt made to criticize on the varying aspects of the mentioned technique and to come across more practical possibilities in the specific field.

Keywords: superimposition ,Anthropology, Photographic superimposition, X-ray

Introduction

The technique of skull superimposition from photographs is one of the most emerging technique in forensic anthropology. Identification by anthropologists using the human face tends to fall in two categories: skull-photo superimposition and forensic image comparison. Here we discuss on the topic skull photo superimposition and its various aspects. By using this method, the deceased one or the unknown can be discovered. A skull, apart from revealing age, sex, and race of a person can also serve as the basis for the cephalic identification. The identification of this skull and the skull/craniofacial reconstruction can be performed by using these methods. This is possible by superimposing the photograph of the individual suspected of belonging to the unidentified skeletal remains over an X-ray of the unidentified skull. Currently various types of skull superimposition or crania superimposition techniques are in practice. The mostly used techniques are photographic superimposition, video superimposition, and Radiographic superimposition (X-ray). Using these techniques the face of the deceased can be recreated and could be identifiable. The life size negative of the skull and the photograph of the missing person are superimposed taking care that the various characteristic features are coinciding with each other. Superimposition is said to be perfect when all the characteristics of the skull match with the negative of the photograph of the missing person or the unidentified person. Even though it has more advantages and reliability over other techniques it also has its negatives. Going through this lets analyses the various aspects of superimposition techniques and also discuss the relevance.

Discussion

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There are mainly two techniques prevails in the anthropology field for craniofacial/skull superimposition. Those are Photographic superimposition and Video superimposition.

Photographic Superimposition

The photographic superimposition is the most widely used technique .This technique was developed in mid-1930’s.Its performed by comparing the life-sized negative with the cranial structure or the model of the same. Recent photograph of the missing person is enlarged to life size taking into account some standard photograph like shirt design, ear rings, nose rings etc. as scale of the person. In the absence of these markings in the photographs, the photograph of the missing person is enlarged to such an extent that the interpapillary distance corresponds with the two orbits of the skull. To get this life sized negative of the skull it is fixed on a stand and viewed through a camera having a ground glass on which salient features of the face of the missing person are marked. The position of the skull is arranged in such a way that it matches the portraits of the missing person on the ground glass of the camera. Both of this life size negative of the skull and the photograph are superimposed taking care that various characteristic features are coinciding with each other. It is said to be a perfect superimposition when all the characteristics of the skull matches the negative of the photograph.

Video Superimposition

It was the most prevailing superimposition technique during the latter half of 70’s in the field of anthropology. Here skull is placed on a rotatable stand and photograph is also fixed under the other camera. Images of skull and photograph are projected on the monitor. By series of blending, fading and sweeping images of skull and photographs are superimposed. All the anatomical landmarks are compared. For this technique equipment’s like skull positioning box, electronic and mixing devices, control panel with joystick levers of momentary paddles which TV monitor and a photo stand for taking the facial photographs are used.

Computer Assisted Superimposition

This is one of the advanced methods used by forensic anthropologists for craniofacial superimposition or face construction to identify the unidentified. Here the skull and facial photograph are digitalized using a computer. Both these images are compared morphologically. Establishing the scale for digitalized skull is performed by converting the actual measurements between the landmarks into the number of pixels on the monitor. Anatomical relationships are evaluated by wiping, fading and fade out. Computer assisted superimposition can be classified into two; one includes a set of computer assisted processes that uses commercial software’s like Photoshop, Coral draw or 3D studio ax to complete the skull face overlay manually in digital form and the latter includes a set of computational intelligence techniques such as genetic algorithms, Multimodal GA, Covariance matrix adaptation evolution strategies and Real coded GA that are used to automate the overlay process.

Radiographic Superimposition (X-Ray)

The Identification of human remains is of importance in medico legal investigations. The comparison ante mortem and postmortem radiographic records is one of the main techniques used for positive identification. The method of direct superimposition of an individual’s lateral skull radiographs using a radiographic subtraction technique is outlined .The errors introduced by superimposition on two different occasions by the same operator are quantified,30 pairs of radiographs being superimposed on the anterior cranial base .

Application

The above mentioned techniques have wide applications in the field of forensics. One of the major application is forensic facial reconstruction for forensic facial approximation. It is the process of recreating the face of an individual (whose identity is often not known) from their skeletal remains through an amalgamation of artistry, forensic science, anthropology, osteology and anatomy. Mainly there are two types of identification i.e.; circumstantial and positive. Circumstantial identification is established when an individual fits the biological profile of a set of skeletal remains. This type of identification does not prove or verify identity because any number of individuals may fit the same biological description. Positive identification is established when a unique set of biological characteristics of an individual are matched with a set of skeletal remains. This type of identification requires the skeletal remains to correspond with medical or dental records, unique ante mortem wounds or pathologies, DNA analysis and still other means.

Types Of Reconstructions

Mainly there are two types of reconstruction: 2D and 3D

Two Dimensional reconstruction; this type of facial reconstruction are based on ante mortem photographs and the skull. This method usually requires the collaboration of an artist and a forensic anthropologist. Recently developed, the F.A.C.E and C.A.R.E.S computer software programmers quickly produce 2D facial approximations that can be edited and manipulated with relative ease. This helps in rapid reconstruction.

Three Dimensional Reconstruction; These type of reconstructions are either 1.Sculptures (made from casts of cranial remains) created with modeling clay and other materials or 2.High resolution, 3D Computer images. Computer programmers create 3D reconstructions by manipulating scanned photographs of the unidentified cranial remains, stock photographs of facial features and other available reconstructions. These computer approximations are usually most effective in victim identification because they do not appear too artificial.

Advancements

The identifications of bodies through the examination of skeletal remains hold a prominent place in field of forensic investigations. The technological advancements in 3D facial acquisition techniques have led to the proposal of a new body identification technique that involves combination of craniofacial superimposition and photogrammetry. This method is done by superimposing various computerized 3D images of skulls onto various photographs of missing people taken while they were still alive. The technique is divided into four phases;

1. Preparatory phase,

2. 3D acquisition phase,

3. Superimposition phase, and,

4. Metric image analysis 3D.

The actual superimposition of images was carried out in fourth step and was done so by comparing the skull images with selected photos .Using specific software, the two images (i.e., 3D avatar and the photo of missing person) were superimposed.

Skull Superimposition Using CT And Presentation Software

The technique of using complex video setups with film editing techniques can be greatly simplified with custom modern CT technology and the PowerPoint presentation software including custom animation. This novel method , using universal technology , quickly and simply replicate the results obtained by the widely accepted but complicated and time consuming video sequencing processes. This can be accomplished using almost any PC and modern CT equipment with minimal man power. A great advantage of this new technique is that it does not require deflating a skull thus permitting examination of a live subject who is unrecognizable due to injury.

NEGATIVES AND AFFIRMATIVES

The main drawbacks of skull superimposition is the practical problems faced during superimpositions:

  • Non availability of a clear photograph
  • The available hazy photograph does not reveal the facial features of the suspected deceased.
  • Missing of bone pieces in facial skeleton and missing of mandible.
  • Teeth less skull with clear ante mortem dental records or dental pattern revealing photographs.
  • Distorted photographs for comparison.

Even though it has certain drawbacks some of its major positives like identification of unknown corpses in a mass destruction field such as arson, landslides etc. makes it more dominant from its demerits.

Conclusion

Skull photo superimposition and craniofacial reconstruction are two important tools for human identification. In many cases the only available link between an unknown and a known person is a photograph. In the case of skull photo superimposition facial images, are typically placed over carefully aligned and sized skull images and the position of specific points is evaluated. Identity is accessed by evaluating the correspondence between specific landmarks on the face and the skull. Current and future researches will likely deal with a number of issues relating to skull photo superimposition including the role of parameters and statistics and with scientific validation. This field has major applications in the present scenario where massive destructions and criminality increases day by day so it requires more advancement.

About The Author

Aneeta Thomas currently studying in the Department of Applied Microbiology and Forensic Science at St. Joseph’s College, Irinjalakuda, Thrissur, Kerala, India.

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