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Forensic facial reconstruction

2007 Schools Wikipedia Selection. Related subjects: Archaeology

   Facial reconstruction of The Spirit Cave Man, one of very few complete
   skeletons found in the United States over 8,000 years old.
   Enlarge
   Facial reconstruction of The Spirit Cave Man, one of very few complete
   skeletons found in the United States over 8,000 years old.

   Forensic facial reconstruction (or forensic facial approximation) is
   the process of recreating the face of an unidentified individual from
   their skeletal remains through an amalgamation of artistry, forensic
   science, anthropology, osteology, and anatomy. It is easily the most
   subjective - as well as one of the most controversial - techniques in
   the field of forensic anthropology. Despite this controversy, facial
   reconstruction has proved successful frequently enough that research
   and methodological developments continue to be advanced.

   In addition to remains involved in criminal investigations, facial
   reconstructions are created for remains believed to be of historical
   value and for remains of prehistoric hominids and humans.

The Daubert Standard

   Full article: Daubert Standard.

   The Daubert Standard is a legal precedent set in 1993 by the Supreme
   Court regarding the admissibility of expert witness testimony during
   legal proceedings. This standard was set in place to ensure that expert
   witness testimony is based upon sufficient facts or data, is the
   product of reliable principles and/or methods (including peer review),
   as well as ensuring that the witness has applied the principles and
   methods reliably to the facts of the case.

   When multiple forensic artists produce approximations for the same set
   of skeletal remains, no two reconstructions are ever the same and the
   data from which approximations are created are largely incomplete.
   Because of this, forensic facial reconstruction does not uphold the
   Daubert Standard, is not included as one of the legally recognized
   techniques for positive identification, and is not admissible as expert
   witness testimony. Currently, reconstructions are only produced to aid
   the process of positive identification in conjunction with verified
   methods.

Positive & Circumstantial Identification

   There are two types of identification in forensic anthropology:
   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, one of the foremost goals of forensic
       science, 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.

   Facial reconstruction presents investigators and family members
   involved in criminal cases concerning unidentified remains with a
   unique alternative when all other identification techniques have
   failed. Facial approximations often provide the stimuli that eventually
   lead to the positive identification of remains.

Types of Reconstructions

   There are two main methods used in forensic facial approximation:
   two-dimensional and three-dimensional.

2D Reconstructions

   Two-dimensional facial reconstructions are hand-drawn portraits based
   on radiographs, 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 programs quickly produce two-dimensional facial
   approximations that can be edited and manipulated with relative ease.
   These programs help speed the reconstruction process and allow subtle
   variations to be applied to the drawing.

3D Reconstructions

   Three-dimensional facial reconstructions are either: 1) sculptures
   (made from casts of cranial remains) created with modeling clay and
   other materials or 2) high-resolution, three-dimensional computer
   images. Like two-dimensional reconstructions, three-dimensional
   reconstructions usually require both an artist and a forensic
   anthropologist. Computer programs create three-dimensional
   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
   picturesque or too artificial.

Superimposition

   Superimposition is a technique that is sometimes included among the
   methods of forensic facial reconstruction. It is only sometimes
   included as a technique because investigators must already have some
   kind of knowledge about the identity of the skeletal remains with which
   they are dealing (as opposed to 2D and 3D reconstructions, when the
   identity of the skeletal remains are generally completely unknown).
   Forensic superimpositions are created by superimposing a photograph of
   an individual suspected of belonging to the unidentified skeletal
   remains with an X-ray of the unidentified skull. If the skull and the
   photograph are of the same individual, then the anatomical features of
   the face should align accurately.

History

   Welcker (1883) and His (1895) were the first to reproduce
   three-dimensional facial approximations from cranial remains. Most
   sources, however, acknowledge His as the forerunner in advancing the
   technique. His also produced the first data on average facial tissue
   thickness followed by Kollmann and Buchly who later collected
   additional data and compiled tables that are still referenced in most
   laboratories working on facial reproductions today.

   Facial reconstruction originated in two of the four major subfields of
   anthropology. In biological anthropology, they were used to approximate
   the appearance of early hominid forms, while in archaeology they were
   used to validate the remains of historic figures. In 1964, Gerasimov
   was probably the first to attempt paleo-anthropological facial
   reconstruction to estimate the appearance of ancient peoples

   Although students of Gerasimov later used his techniques to aid in
   criminal investigations, it was Wilton M. Krogman who popularized
   facial reconstruction’s application to the forensic field. Krogman
   presented his method for facial reconstruction in his 1962 book,
   detailing his method for approximation. Others who helped popularize
   three-dimensional facial reconstruction include Cherry (1977), Angel
   (1977), Gatliff (1984), Snow (1979), and Iscan (1986).

Technique for Creating a 3D Clay Reconstruction

   NOTE: Because a standard method for creating three-dimensional forensic
   facial reconstructions has not been widely agreed upon, multiple
   methods and techniques are used. The process detailed below reflects
   the method presented by Taylor and Angel from their chapter in
   Craniofacial Identification in Forensic Medicine, pgs 177-185. This
   method assumes that the sex, age, and race of the remains to undergo
   facial reconstruction have already been determined through traditional
   forensic anthropological techniques.

   The skull is the basis of facial reconstruction; however, other
   physical remains that are sometimes available often prove to be
   valuable. Occasionally, remnants of soft tissue are found on a set of
   remains. Through close inspection, the forensic artist can easily
   approximate the thickness of the soft tissue over the remaining areas
   of the skull based on the presence of these tissues. This eliminates
   one of the most difficult aspects of reconstruction, the estimation of
   tissue thickness. Additionally, any other bodily or physical evidence
   found in association with remains (e.g. jewelry, hair, glasses, etc)
   are vital to the final stages of reconstruction because they directly
   reflect the appearance of the individual in question.

   Most commonly, however, only the bony skull and minimal or no other
   soft tissues are present on the remains presented to forensic artists.
   In this case, a thorough examination of the skull is completed. This
   examination focuses on, but is not limited to, the identification of
   any bony pathologies or unusual landmarks, ruggedness of muscle
   attachments, profile of the mandible, symmetry of the nasal bones,
   dentition, and wear of the occlusal surfaces. All of these features
   have an effect on the appearance of an individual’s face.

   Once the examination is complete, the skull is cleaned and any damaged
   or fragmented areas are repaired with wax. The mandible is then
   reattached, again with wax, according to the alignment of teeth, or, if
   no teeth are present, by averaging the vertical dimensions between the
   mandible and maxilla. Undercuts (like the nasal openings) are filled in
   with modeling clay and prosthetic eyes are inserted into the orbits
   centered between the superior and inferior orbital rims. At this point,
   a plaster cast of the skull is prepared. Extensive detail of the
   preparation of such a cast is presented in the article from which these
   methods are presented.

   After the cast is set, colored plastics or the colored ends of safety
   matches are attached at twenty-one specific “landmark” areas that
   correspond to the reference data. These sites represent the average
   facial tissue thickness for persons of the same sex, race, and age as
   that of the remains. From this point on, all features are added using
   modeling clay.

   First, the facial muscles are layered onto the cast in the following
   order: temporalis, masseter, buccinator and occipito-frontals, and
   finally the soft tissues of the neck. Next, the nose and lips are
   reconstructed before any of the other muscles are formed. The lips are
   approximately as wide as the interpupillary distance. However, this
   distance varies significantly with age, sex, race, and occlusion. The
   nose is one of the most difficult facial features to reconstruct
   because the underlying bone is limited and the possibility of variation
   is expansive. The nasal profile is arbitrarily determined by projecting
   two lines from the midline of the skull unless any obvious bony
   asymmetry is present, in which case accommodating adjustments to the
   possible projection are made.

   The muscles of facial expression and the soft tissue around the eyes
   are added next. Additional arbitrary measurements are made according to
   race (especially for those with eye folds characteristic of Asian
   descent) during this stage. Next, tissues are built up to within one
   millimeter of the tissue thickness markers and the ears (noted as being
   extremely complicated to reproduce) are added. Finally, the face is
   “fleshed,” meaning clay is added until the tissue thickness markers are
   covered, and any specific characterization is added (for example, hair,
   wrinkles in the skin, noted racial traits, glasses, etc.).

Problems with facial reconstruction

Insufficient tissue thickness data

   There are multiple outstanding problems associated with forensic facial
   reconstruction. Probably the most pressing issue relates to the data
   used to average facial tissue thickness. The data available to forensic
   artists are still very limited in ranges of ages, sexes, and body
   builds. This disparity greatly affects the accuracy of reconstructions.
   Until this data is expanded, the likelihood of producing the most
   accurate reconstruction possible is largely limited.

Lack of methodolocial standardization

   A second problem is the lack of a methodological standardization in
   approximating facial features and individuating characteristics.
   Forensic anthropologists and artists have published individual
   techniques used in their own practices. However, a single, official
   method for reconstructing the face has yet to be recognized. This also
   presents major setback in facial approximation because facial features
   like the eyes and nose and individuating characteristics like hairstyle
   - the features most likely to be recalled by witnesses - lack a
   standard way of being reconstructed. Without consistency and a standard
   method for approximating these features, it will remain very difficult
   for forensic reconstruction to earn wide recognition as a legitimate
   form of forensic identification.

Subjectivity

   Reconstructions only reveal the type of face a person may have
   exhibited because of artistic subjectivity. The position and general
   shape of the main facial features are mostly accurate because they are
   greatly determined by the skull, but subtle details like certain
   wrinkles, birthmarks, skin folds, the shape of the nose and ears, etc,
   are unavoidably speculative because skeletal remains leave no evidence
   of their appearance. The success of reconstruction depends as much upon
   the circumstances pertaining to the subject under investigation as it
   does upon the accuracy of the technique.
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