In the Dock: Chimeric Image Composites Reduce Identification Accuracy

The aim of presenting chimeric images (formed from opposing halves of a pair of same or different faces) in court settings is to optimise the accuracy of identification decisions based on CCTV evidence. The experiments reported here examined the utility of this technique. Experiment 1 examined the accuracy of face matching with vertically split, aligned chimeric images, misaligned hemi-faces and full-face images. Experiment 2 replicated the first experiment but replaced the misaligned images with opposing hemi-faces separated by a gap. The final experiment used horizontally split faces. All three experiments showed that matching was less accurate with aligned chimeric images than with full-face images. Furthermore, the pattern of responses obtained with chimeric images differed significantly from full-face matching and misaligned/separated hemi-face matching. Chimeric images produced a bias towards same responses even when the face halves were different. The results suggest caution in the use of chimeric images in court.