AbstractIn a criminal investigation, witnesses may get asked by the police to provide a
perpetrator’s description or to generate a composite image of the perpetrator’s face. Due to their elevated vulnerability to victimisation people with a learning disability (LD) may be more likely than other members of the wider community to find themselves in such situations. Research regarding face recognition and description abilities of this group has been to some extent neglected in the eyewitness research literature. Consequently, guidance for practitioners on how to effectively generate facial composite images with LD witnesses is limited. The current research addresses this issue, by investigating basic and applied face recognition and description abilities in individuals with mild learning disabilities (mLD) during a series of experimental studies. Moreover, potential facilitating measures are introduced and assessed.
Five studies were conducted during the course of this thesis. In the first study a survey was designed to collect information on currently used composite systems by UK law enforcement agencies and how operators perceive and treat witnesses with LD. The survey findings confirmed the initial assumption that individuals with LD may indeed find themselves in the situation of having to describe a perpetrator’s face to an investigative officer. Furthermore, the results emphasised the lack of guidance available to operators on how to best meet the special needs of this particular witness population.
Study 2 investigated basic face recognition and description abilities in people
with mLD and revealed that overall they performed at a lower level than the non-LD controls. Despite this finding, mLD individuals as a group performed above chance levels and they displayed variability in performance depending on the introduced measures.
Studies 3 and 5 investigated these abilities in a more applied setting, namely
during the construction of facial composites with contemporary facial composite
systems. Study 3 revealed that composites generated with the E-FIT system, a featural system, were considerably poorer than those created by their non-LD counterparts.
Studies 4 and 5 attempted to improve mLD individuals’ performance by applying
visual prompts and by using a more holistic facial composite system, i.e. EvoFIT.
There was little evidence of the former being advantageous for witnesses with mLD, however, EvoFIT significantly enhanced composite construction abilities in the mLD participants.
Finally, the practical and theoretical implications of the main findings are discussed.
|Date of Award||Oct 2010|
|Supervisor||Derek Carson (Supervisor) & Fiona Gabbert (Supervisor)|
- Intellectual disabilities
- Facial composite systems
- Face recognition