The impact of external facial features on the construction of facial composites

Abstract

Witnesses may construct a composite face of a perpetrator using a computerised interface. Police practitioners guide witnesses through this unusual process, the goal being to produce an identifiable image. However, any changes a perpetrator makes to their external facial-features may interfere with this process. In Experiment 1, participants constructed a composite using a holistic interface one day after target encoding. Target faces were unaltered, or had altered external-features: (i) changed hair, (ii) external-features removed or (iii) naturally-concealed external-features (hair, ears, face-shape occluded by a hooded top). These manipulations produced composites with more error-prone internal-features: participants’ familiar with a target’s unaltered appearance less often provided a correct name. Experiment 2 applied external-feature alterations to composites of unaltered targets; although whole-face composites contained less error-prone internal-features, identification was impaired. Experiment 3 replicated negative effects of changing target hair on construction and tested a practical solution: selectively concealing hair and eyes improved identification.

Practitioner Summary: The research indicates that when a target identity disguises or changes hair, this can lead to a witness (or victim) constructing a composite that is less readily identified. We assess a practical method to overcome this forensic issue.

Abbreviation: GEE: Generalized Estimating Equations

Keywords:

• Facial composite
• altered external-features
• hair
• holistic face processing
• witness

Notes

1 Although not tested here, it is also conceivable that the array should promote better recognition of offenders who change their hair after a crime has taken place. In this situation, the composite’s hair would be presumed accurate at the time of the crime, but not when identification is attempted. Thus, showing the composite with hat would usefully hide the feature that had been changed after face construction.