Forensic facial reconstruction
2007 Concise Encyclopedia. Related subjects: Archaeology
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.