Skull Superimposition and Facial Reconstruction

The scientific skill of reconstructing an individual’s facial appearance from the skull for the purpose of personal identification is known as forensic facial reconstruction. It’s a forensic technique that is utilized when there are unidentified remains in a crime scene. A sculptor who is an expert in facial anatomy generally performs facial reconstruction. It is not necessary for this sculptor to be a forensic artist. The sculptor will collaborate with forensic anthropologists to analyse the skeleton’s characteristics, which will ultimately aid in determining the victim’s age, gender, and ancestry. Anatomical characteristics such as facial asymmetry, evidence of traumas such as a broken nose, or teeth that were lost before death can also be revealed by sculpting. It is one of the most common method used to identify unknown human remains when other methods fail.

In a forensic setting, the ultimate goal of facial reconstruction is to reproduce the look that most closely matches the deceased’s original face, in order to stimulate public recognition and, eventually, personal identification. However, it is important that facial reconstruction should be used in conjunction with other well-established procedures such as dental records and DNA analysis for accurate identification as it is not a positive identification on its own.

Hence, Facial reconstruction is a combination method which constitutes both scientific and artistic skills. It is used in Forensic Anthropology as well as Archaeology. Several reconstruction approaches have been developed throughout the years, all of which are based on the relation between the soft facial tissues and the underlying skull.

HISTORY OF FACIAL RECONSTRUCTION

1.)Wilhelm His, a German anatomist, performed the first facial reconstruction in 1895.He reconstructed the face of a German composer Johann Sebastian Bach. He used data from a small number of cadavers to build a bust of musician Johann Sebastian Bach onto a copy of the skull, which he collaborated on with sculptor Karl Seffner.

2.) Welcker, a German physiologist and anatomist, examined the depth of penetration of a tiny surgical blade into several anthropometric landmarks on the face after documenting typical tissue depth thickness from cadavers. This procedure is known as the “Welcker Facial Reconstruction Technique.”

3.) Plaster skulls with shells in eye sockets were discovered under the floors of homes dating from 7500 to 5500 BC (the Pre-Pottery Neolithic B Period).

4.) Wax models were employed by artists such as Verrocchio, Michelangelo, and Versalius to chronicle their works.

5.) In 1898, Kollmann and Buchly produced a facial approximation of Dante from tissue depth measurements taken at ten midline and eight lateral points of twenty-one male and four female cadavers ranging in age from 17 to 72 years, resulting in mean measurements for 45 male and eight female European White cadavers.

6.) Wilton Maria Krogmann later proposed five key principles to modify the techniques of reconstruction of soft tissues in 1946, namely the relationship of the eyeball to the orbit, shape of the nose tip, placement of the ear, the mouth breadth, and the ear length.

7.) Facial reconstructions began to be utilised in museums at the turn of 20^th century.

8.) With the advancement of 3D technology, computerised facial reconstruction software that is quick, efficient, and cost-effective has been developed. The programme mimics the manual facial reconstruction process. The use of computers in reconstruction was initially investigated.

TYPES OF FACIAL RECONSTRUCTION TECHNIQUES

1.) Two-dimensional facial reconstruction: Recreation of face from the skull is based upon the estimation of soft tissue depth. Karen Taylor first developed this approach in the 1980s in Austin, Texas. This approach necessitates collaboration between an artist and a forensic anthropologist for facial reconstruction, and is based on ante mortem photos and the skull to be recreated. This technique is also used to identify the deceased from their skeletal remains. Various computer software systems such as CARESTM or CARES (Computer Assisted Recovery Enhancement System) and FACES (Forensic Anthropology Computer Enhancement System), may now swiftly create 2D reconstructions that can be altered and changed. These work by digitalising radiographs, photos, and images of skulls and creating an electronically changed replica of the image. These software’s speeds up the reconstruction process and also produce more generic images.2-D techniques are cost effective and time saving.

2.) Three-dimensional facial reconstruction: An artist and a forensic anthropologist are required for this method also. Manual techniques involve applying clay, plastic, or wax directly to the victim’s skull, or more commonly, a duplicate of the victim’s skull that must be recognised. This approach is similar to the two-dimensional method as both the techniques use tissue depth markers of particular lengths to indicate soft tissue depths. 3-D technique involves utilising generic measures defined by age, sex, and ancestry to place the tissue markers in particular locations and depths on the skull. These markers are inserted into tiny holes on the cast of skull at specific points which are known as landmarks. Computer software creates a reconstruction utilising scanned and stock images in the digitalised and automated approach.

3.) Superimposition: It is not often included as a technique because investigators must already have some information of the identification of the skeletal remains with which they are working (as opposed to 2D and 3D reconstructions, when the identity of the skeletal remains are generally completely unknown). Superimposing an image of an individual suspected of belonging to the unidentified skeletal remains over an X-ray of the unidentified skull creates forensic superimpositions. The anatomical characteristics of the face should match correctly if the skull and the image are of the same person.

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SKULL AND FACE : ANATOMICAL RELATIONSHIPS

1.) Facial soft tissue thickness: One of the most significant variables in recreating the face of an unknown skull is the thickness of facial soft tissue. Soft-tissue thickness is measured on the different anthropometric sites of the head using a variety of techniques, including puncturing, radiography, ultrasonic probing, and computed tomography. For each race, data on the thickness of face soft tissue has been gathered: Mongoloid, Negroid, and Caucasoid. Examiners must first analyse the shapes of both the skull and the face, and then take into consideration soft-tissue thickness at various locations and evaluate its individual variation when using superimposition.

2.) Locational relationships between the skull and the face: This is based on relation of: from the eye to the orbit in the vertical position, teeth to lips at rest, the line created by the bite seems to correspond with the oral slit, ear to porus acusticus externus.

METHODS OF MANUAL THREE DIMENSIONAL RECONSTRUCTION TECHNIQUES (3-D)

1.) Anthropometrical American Method/ Tissue Depth Method (1946): This technique was developed by Krogmann by utilising soft tissue depth data. It is one of the oldest and was the most common method used by law enforcement agencies during the 1940’s. Needles, X-rays, and ultrasound were used to acquire fine measurements. This approach is no longer favoured because it needs highly skilled individuals for recording the face muscles in a precise anatomical manner.

2.) Anatomical Russian Method (1971): This technique was developed byGerasimov by utilising the facial muscles in anatomical positions. The technique is not preferred these days. Reconstruction was accomplished using this approach by layering muscles, glands, and cartilage onto the skull. This approach is significantly slower than the American method, and it necessitates a higher level of anatomical understanding. This approach has been used to reconstruct fossilised skulls.

3.) Combination Manchester Method/ British Method (1977): This technique was developed by Neave and it is one of the most preferred and accepted method today. It is one of the most accurate and best method for a positive identification of an individual. This technique utilises both soft tissue thickness as well as facial muscles for reconstruction purposes.

4.) Skull photo/video superimposition: When ante-mortem pictures of one or more probable decedents are available, this approach is beneficial. It includes superimposing important anatomical markers from a subject’s facial picture onto a photo of the appropriately aligned skull.

Photographic Superimposition: The examiner must always expand the comparison pictures to the size of the unknown skull before positioning the skull in the same orientation as the facial photographs while doing photographic superimposition. Enlarging facial photos has been done using measurable items for the enlargement scale, facial proportions, and distances.

Video Superimposition: Video superimposition has been claimed to have a significant benefit over traditional photographic superimposition in that comparisons may be performed more quickly and in greater detail than with static images. A skull-positioning rest, two video cameras (1 and 2), a video image mixing equipment, a TV display, and a videotape recorder are all part of the video superimposition system.

Computer-assisted superimposition: Computer-assisted superimposition has been a common way of identifying the unknown skull as computer technology develops. From the standpoint of identification approach, computer-assisted superimposition may be categorised into two kinds:

• The first technique is to use a video computer with suitable software to digitise the skull and facial photos, and then to compare the two images morphologically using image processing. Converting the actual measurement between the land-marks (e.g. zygion-zygion, nasion-gnathion, etc.) into the number of pixels on the display is used to provide a scale for the digitised skull picture.
• The second technique is to use morphometric testing to assess the fit between the skull and the face picture. The assessment of skull identification will be more objective and trustworthy if quantitative data based on morphometric studies is acquired in addition to the anatomical and anthropometric evaluation.

5.) Computerized 3D Forensic Facial Reconstruction (1980’s): With the advent of 3D technology, a computer-aided forensic facial reconstruction approach that is rapid, efficient, and cost effective has been developed. The operator utilised 3D digital models and handmade clay model techniques in this procedure. To model the face onto the skull, some computerised systems employed 3D animation software (Free Form Modelling PlusTM; Sensable Technologies, Wilmington MA), while others used a virtual sculpting system with haptic feedback (Phantom DesktopTM Haptic Device; Sensable Technologies). During analysis, the haptic feedback system can feel the surface of the skull and give essential skeletal data for facial reconstruction, such as muscle attachment strength, eye location, and malar tubercle position. However, this approach needs both anthropological and computer modelling abilities. It reduces the subjectivity and competence of the practitioner.

Computerized approaches may be repeatable, quick, and exact, but the quality of the reconstruction will be harmed if they use outdated data.

Even though a fair match can be observed in the skull-photo superimposition picture, it is widely acknowledged that the unknown skull without the mandible cannot be conclusively identified as the assumed individual. To get any level of confidence, the entire skull must be examined. The skull-photo superimposition should be able to establish if the skull and facial image belong to the same individual. In general, the skull-photo superimposition is seen to be more beneficial for exclusion reasons since the skull and facial image can be positively identified as not belonging to the same person. However, if the skulls are well matched, the only conclusion is that the skull is that of the pictured individual. This is due to the potential that this skull matches the face of another person in a photograph, or that another skull of similar size and contour matches the face of the photographed individual.

Thus, for both legal and humanitarian grounds, facial reconstruction techniques are an important tool in the identification of human remains. It also makes visual identification by a person’s relatives and acquaintances easier. The introduction of computers and specialised software has ushered in a new era, enhancing all of the capabilities of this technique.

Authored By:

Akhila Prabhakar

BSc Forensic Science

JAIN(Deemed-to-be-University)