Five years ago, when an unidentified skull needed a face, a forensic artist would use general UK and North American population data and put pencil to pad or mould a 3D facial reconstruction using clay.
These days, the latest developments in 3D technology and computer graphics mean that the facial reconstruction no longer has to be performed manually. Forensic artists at the South African Police can now use South Africa specific data for their cases rather than North America or British data.
Although forensic sketches are still used, computer software that generates 3D images of a reconstructed face have become the preferred method. The use of computer technology also means more precise and objective age progression techniques are used to predict a missing person’s appearance, based on their age.
Recently, our research has provided data on the craniofacial proportions, facial growth and tissue thickness of all South African children between the ages of six and 13. These tissue thickness values are important as they provide a more realistic representation when a facial reconstruction is done to aid in determining the identity of the victim.
The challenge in solving a cold case
A significant number of child homicides are underreported because the perpetrators conceal the crime. As a result, the remains of many children are only discovered some time later.
When skeletal remains of a child are found, the police’s forensic artists can use facial reconstruction to help identify the remains. This reconstruction can also be placed in the media to make the public aware of the case.
Facial reconstruction uses the relationships between the facial features, subcutaneous soft tissues and underlying bony structure of the skull to recreate the face. It fuses artistry with forensic science, anthropology, osteology and anatomy.
For children of European ancestry, facial reconstruction was based on European standards. A study on white British and North American children suggested similarities across some regions of the world for children of European ancestry.
In South Africa, facial reconstructions for black children were problematic because until recently forensic artists only had the facial soft tissue thickness data for children of European and American descent. Previous research has shown that tissue thickness data from other regions of the world cannot be used to adequately reconstruct faces of Black South Africans.
Coloured children also pose a problem – there are significant differences between the tissue thickness of adult black South Africans to a coloured sample.
The dilemma with missing children
In cases where the remains of the missing child have not been found, forensic artists use ageing techniques to project how the child’s face would have aged during the time they have been missing. Many of these cases rely only on old photographs of the missing child.
The challenge in such cases is that changes in the face and head of the child as a result of facial growth in their prepubescent and pubescent years complicate the age progression. This impacts on the prediction of the child’s facial features. Previously, forensic artists used photographs of the parents of the missing child to project how the missing child might have aged but this was criticised as being too subjective.
Although excellent studies around general growth were conducted in South Africa, facial growth and facial changes during growth were not specifically addressed. As a result, no data on the craniofacial dimensions and facial growth changes in South African children were available until this year.
Our research describes patterns of facial growth in primary school children using craniofacial indices and face shape changes at various ages by means of geometric morphometric analyses.
This means that more precise and objective age progressions techniques can now be used performed to predict a missing child’s current appearance. These methods provide growth patterns which can be used by the police to predict, using an earlier photograph, what a missing child might look like years later.
Not one size fits all
Although the data set will primarily be used to tackle crimes against children, it can also have wider application.
It could be used in reconstructive maxillofacial surgery and orthodontic treatment and diagnosing syndromes based on facial dysmorphology such as Fetal Alcohol Syndrome. This is because it is specific to South African children and documents the changes in their face shapes at various ages.
Most importantly, however, providing data on craniofacial proportions, facial growth and facial soft tissue thickness of South African children between the age of six and 13, reflects progress in this field. It will greatly improve the reliability and validity of craniofacial reconstructions and age progression of missing children.
Nanette Briers received funding from the National Research Foundation. Any opinions, findings and conclusions expressed in this paper are those of the authors and therefore the NRF does not accept any liability in regard thereto.
Maryna Steyn receives funding from the National Research Foundation of South Africa.
Authors: The Conversation