A facial composite is a graphical representation of one or more eyewitnesses' memory of a face, as recorded by a composite artist. Facial composites are used mainly by police in their investigation of crimes. These images are used to reconstruct the suspect's face in hope of identifying them.
Methods
PhotoFIT generation
Construction of the composite was originally performed by a trained artist, through drawing, sketching, or painting, in consultation with a witness or crime victim. Subsequently, techniques were devised for use by those less artistically skilled, employing interchangeable templates of separate facial features. The first such mechanical system, called "Identikit", was introduced in the U.S. in 1959; it used drawings of facial features on transparent acetate sheets that could be superimposed on one another to produce the composite image. In 1970, a system called "Photofit", which aimed for greater realism by using actual photographs of facial features, was introduced in the U.K. 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.
Evolutionary systems
Until quite recently, the facial composite systems used by international police forces were exclusively based on a construction methodology in which individual facial features 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 converges towards an increasingly accurate image. Three such systems have come from academic beginnings, EFIT-V from the University of Kent; EvoFIT from the University of Stirling, the University of Central Lancashire and the University of Winchester; and ID from the University of Cape Town, South Africa. GFE is an experimental evolutionary face compositing system using image gradient instead of luminance to represent faces, which seems to produce better quality composites.
Research
A general review of research into the evaluation of mechanical template techniques may be found in Davies and Valentine. 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. and. The systems used in the UK have been subjected to a number of academic studies. These have typically shown that E-FIT and PRO-fit produce composites that are correctly named, either immediately or a few hours after construction, about 20% of the time, Bruce et al., Davies et al. and Frowd et al. ). When witnesses in these studies are required to wait two days before constructing a composite, which matches real use more closely, naming falls to a few percent at best. The reason for the low level of naming from these systems appears to be that witnesses are unable to accurately construct the internal features of the face after long delays, the region that is important for recognition by another person later. Evolutionary systems show a marked improvement in accuracy. In academic trials, research on a fairly-recent version of the EvoFIT system has shown correct naming levels of about 30% after a 2-day delay. Using more-recent construction techniques, the performance increased to 45% correct naming. Using the very latest system, interview and enhancement techniques, naming of an EvoFIT composite is 74% correct. Appropriately, the system does appear to behave more like a face recognition than a face recall system Accompanying the development of EvoFIT have been new approaches in the type of interview administered to eyewitnesses prior to face construction. Similarly in extensive field use EFIT-V has shown a 40% naming rate over an 18-month period with 1000 interviews. The EvoFIT system has been similarly evaluated in formal police field-trials. These evaluations have reported a much higher naming rate for EvoFIT composites but, using the latest interview techniques, a suspect arrest rate of 60%. This latest police field trial has also indicated that an EvoFIT directly leads to the arrest of a suspect and then a conviction in 29% of cases. There have been many notable successes - for example, in this investigation, EvoFIT has directly led to the arrest of a serial rapist.
Usage
While the classic use of the facial composite is the citizen recognizing the face as an acquaintance, there are other ways where a facial composite can prove useful. The facial composite can contribute in law enforcement in a number of ways:
Warning vulnerable population against serial offenders.
Facial composites of various types have been used extensively in those television programs which aim to reconstruct major unsolved crimes with a view to gaining information from the members of the public, such as "America's Most Wanted" in the US and "Crimewatch" in the UK.
Notable cases
These notable cases had facial composites assist in identifying the perpetrator:
