|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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the skeletal structure
|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.
| 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.
| 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.
|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.
|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.
|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.
The Skeletal Structure
|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.
| 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.
|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.