What is facial mapping?
Imagery relating to a crime is frequently of a quality that requires interpretation to assist the courts in cases of disputed identity.
Facial mapping, (also referred to as Facial comparison), is the comparison of two of more images (photographic, video or otherwise) of individuals to determine whether or not they are of the same person. (Other body parts, as appropriate, may also be examined in a similar fashion).
What can it do and what are its limitations?
The quality of the imagery available for examination inherently dictates the scope of the examination and ultimately the weight of the conclusion.
Because of inherent limitations of detail, facial mapping cannot be used to conclusively identify someone. It is recognised that two people can share similar facial proportions and morphology. Indeed, on poor quality material it can be difficult to distinguish between two people of similar appearance.
In the absence of any significant differences, rather than providing conclusive identification evidence, this evidence can be a powerful corroborative tool, giving support to other existing evidence and assisting the court in extracting the maximum amount of information from the imagery available.
The discovery of a single difference that cannot be otherwise explained can exclude someone as a candidate for a suspect.
Our experts combine their anatomical and imagery interpretation expertise to produce expert reports and provide expert testimony on behalf of prosecution or defence agents.
There are 3 comparative tests are generally held to be valid for imagery comparisons of facial features:
Photogrammetry (sometimes referred to as photo-anthropometry) involves comparing the spatial proportions of facial features and if possible, measurements of distances and angles between facial landmarks are taken in an attempt to quantify any differences/similarities
Morphological examination involves describing the shape and form of facial features. The method is based upon subjective judgments of facial features
Superimposition (of one image upon another) involves wiping, fading or flickering from one video image to another
The imagery available for examination dictates which of these tests can meaningfully be conducted and elimination is the fundamental aim of the process at all stages.
How are conclusions expressed?
It is not possible to quantify the likelihood of two images being of the same person, in the absence of significant differences, an accepted scale is used by practitioners in this field (endorsed by the Forensic Imagery Analysis Group FIAG):
Lends no support
Lends limited support
Lends moderate support
Lends strong support
Lends powerful support
At present there is no database, which records the incidence of specific features as they appear in the population. This scale of conclusions therefore does not have any statistical foundation. Rather, it is an expression of subjective opinion, informed by experience.
Home Office (ACPO: www.acpo.police.uk
BAHID (FIAG): www.bahid.org
National Policing Improvement Agency: www.npia.police.uk
Related services offered by LGC
Advise on the suitability of imagery to provide identification evidence.
We can advise on the importance of obtaining and having access to the original imagery exhibit and assess whether the imagery available is suitable for facial mapping purposes and if so how to ensure that we as practitioners can provide best evidence for you.
It should be noted that the outcome of any facial mapping evidence is different to that of an eyewitness or someone who knows the offender and recognises them.
Photographing the suspect to obtain the best possible comparison imagery.
The scope, and possibly the resulting weight of conclusion, is dependent on the quality and suitability of the imagery available for examination.
Photographing and/or videoing the individual directly ensures that we have the optimal comparison imagery.
In rare circumstances, an on-site reconstruction may be the best solution. In this instance, we would work with you and other relevant people to ensure that such an undertaking was carried out in an appropriate and professional manner.
We can travel to a location of your choosing, including police stations and prisons if necessary – quotes upon request.
We can provide a professional, written critique of the methodologies, findings and conclusions of other expert reports.