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| Facial
Reconstruction |
| Uncovering skeletons used to mean
very little could be done to determine who the victim was and if appropriate,
who the murderer was. However, with growing technology and experience
of years, facial reconstruction now provides an answer to such mysteries.
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Select one of the following topics for more information:
--> Reconstruction
in clay
--> Beginning
the reconstruction
--> Facial
features
--> The
face
--> Limitations
--> Computer
facial reconstruction
--> Acquiring
the skeletal structure
--> Muscle
and skin
--> Colour
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| Reconstruction
In Clay |
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| Once the skin and flesh has rotted
away from the skull of a corpse, their character and physical appearance
disappear along with it. It then becomes the job of forensic anthropologists,
sculptors and creative artists, to reconstruct a life like form of
what the person looked like from the skeleton and sometimes, remaining
parts of a skeleton. Clay is a common form of reconstruction. |
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| Beginning
the Reconstruction |
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In order to reconstruct
a life-like face, sculptors need to know the depth of skin that
overlays the skull. Sculptors usually begin sculpting with 20
to 35 tissue layers, scattered all over the face. The main heavily
concentrated depths are situated around the mouth and in between
the eyes. Facial depth measurements are available for male and
female, certain ages, racial groups, thin people and obese people.
Small pegs are used as facial depth indicators and are fixed
into the skull or otherwise into a cast of the skull. Strips
of clay that have been made to match the height of the pegs
are then placed between them and once the strips are in place,
clay is used to fill the gaps between each peg. |
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The effectiveness of clay reconstruction depends greatly on
the skill of the sculptor. Photo courtesy of Martin
Evison. |
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| Facial
Features |
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| The sculptor is
then able to start work on the eyes, mouth, ears, nose, chin,
jaw and cheeks, as these are the aspects of the face that give
the most character, but are also the parts that perish most
quickly as the body decays. Sculptors rely on certain rules
during the reconstruction of a face, for example, the width
of the nose is the same as the distance between the inner corner
of the eyes and the corners of a person's mouth lie below the
inner boarders of the iris. Ears are seen as being roughly
the same length as the nose, though elderly people usually have
longer ears. Once the facial features are complete, the sculptor
makes a mould from the clay head using a plaster of Paris silicone
rubber. |
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The facial features of a victim provide the most infsormation
on identity. Photo courtesy of www.imageafter.com.
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| The
Face |
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| Now, the reconstruction of the face
involves the task of building the muscles around it. Sculptors must
approximate the muscle structures by noting the shape and size of
certain facial bones, as these will directly affect the shape of the
muscles previously attached to them. Using their experience, the sculptors
are able to build the face by shaping each of the muscles and then
fixing each one in its place on the skull. The final step is to cover
the clay muscles with a layer of clay skin, which is smoothed over
so that it resembles real skin. |
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| Limitations |
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| However experienced the sculptor is,
there are certain accuracy limits that occur during the reconstruction
of a face. Sculptors can only guess hairstyles and cannot create the
expressions on a persons face that make the sculpture completely life
like. However, a sculpture is successful if it aids in jogging someone's
memory or can narrow down a search by excluding anyone whose face
does not resemble the reconstructed face. |
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| Computer
Facial Reconstruction |
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| Computer facial reconstruction has
developed far enough to allow a virtual form of reconstructing the
face from a skull, making it easy and efficient to travel from computer
to computer. Such software allows for a 3D image/structure of the
finished face to be rotated and moved around on a monitor. |
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| Acquiring
The Skeletal Structure |
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| Using computer facial reconstruction
does not require artistic skill, but it does require skills of a different
sort. There is no standard method of computer facial reconstruction
but the initial data and facial shape comes from a 3D scan of the
skull. This process is non-destructive to the skull and involves the
skull rotating on a turning table whilst a laser scanner lights up
a thin perpendicular strip. Mirrors located on either side
of the turning table reflect the images from the lit up area to sensors.
The data that the scan produces allows a controlling program to determine
the distances of each point located on the skull. This then creates
a digitalised model of the skull that is easily and freely rotated
on the computer screen. |
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| Muscle
and Skin |
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Applying muscle and
skin to the bone requires computer tomography (CT) scans
of actual living people, which acquire images showing where
bones cast shadows onto the skull and record hard/soft tissue
(bones and flesh) in a 3 dimensional, view. Using CT scans,
data files record the shape of the skull as well as the tissue
depth. Forensic anthropologist's knowledge is also utilised
in choosing an appropriate form of CT scan. Any clothing found
with the bones can provide a clothing size, which is useful,
as it allows scientists to adjust any tissue depth measurements
to account for obesity or thinness. Merging the two scans, the
CT scan is applied to the digital scan of the skull, becoming
two skulls on top of each other. At this stage of the process,
the two skulls are different shapes. The computer program distorts
the skulls' marks on both so they match each other and at the
same time, distorting the facial tissue properties, creating
a facial shape that resembles the victim. |
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CT scans provide the latest technology in the reconstruction
of an unknown identity. Photo courtesy of Martin
Evison. |
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| Colour
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| CT scans cannot record vital surface
detail such as hair, skin and eye colour, so these aspects of persons
face must be added. This involves borrowing the physical features
of a living person in order to paint these features onto the 3D model.
A person who has similar age, racial qualities, and build as the modeled
skull is used in a 3D rendering process called 'colour mapping'. This
process involves photographing the face of the person with similar
qualities and using software to merge the three views into one strip
that is put onto the computer to complete the reconstruction. The
final result can be viewed and turned on the screen. Like clay facial
reconstruction, the method does have its accuracy limitation. Nose,
mouth and ear shape are largely down to guessing, however, lighting
conditions and the ability to view the face from any angle makes computer
facial reconstruction very lifelike and helpful during investigations. |
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