Forensic sketch

A facial composite is a graphical representation of an eyewitness's memory of a face, as recorded by a composite artist. Facial composites are used mainly by police in their investigation of (usually serious) crimes. These images are also used to reconstruct the suspect's face in hope of identifying them.

Construction of the composite was originally performed by a trained artist, through drawing, sketching, or painting, in consultation with a witness or crime victim. In the 1970s techniques were devised for use by those less artistically skilled, employing interchangeable templates of separate facial features, such as "Photofit" in the UK, Smith & Wesson's "Identi-Kit" in the U.S. and PortraitPad.

In the last two decades, a number of computer based facial composite systems have been introduced; amongst the most widely used systems are SketchCop FACETTE Face Design System Software, "Identi-Kit 2000", FACES, E-FIT and PortraitPad. In the U.S. the FBI maintains that hand-drawing is its preferred method for constructing a facial composite. Many other police agencies, however, use software, since suitable artistic talent is often not available.

Until quite recently, the facial composite systems used by international police forces were exclusively based on a construction methodology in which individual facial features (eyes, nose, mouth, eyebrows, etc.) are selected one at a time from a large database and then electronically 'overlaid' to make the composite image. Such systems are often referred to as feature-based since they essentially rely on the selection of individual features in isolation. However, after a long period of research and development work conducted largely within British Universities, systems based on a rather different principle are finding increasing use by police forces. These systems may be broadly described as holistic or global in that they primarily attempt to create a likeness to the suspect through an evolutionary mechanism in which a witness's response to groups of complete faces (not just features) converges towards an increasingly accurate image. Three such systems have come from academic beginnings, EFIT-V from the University of Kent; EvoFIT (http://www.EvoFIT.co.uk) from the University of Stirling, the University of Central Lancashire (UCLan) and the University of Winchester; and ID from the University of Cape Town, South Africa.

A general review of research into the evaluation of mechanical template techniques may be found in Davies and Valentine (2006). A review of research into more modern 'feature' and 'recognition' systems, and into methods for improving the effectiveness of composites, may be found in Frowd et al. (2008) and (2009).

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