Assessment of bruise age on dark-skinned individuals using tristimulus colorimetry

Abstract

Introduction Studies on the ageing of bruises have been reported on Caucasians or individuals of fair ethnicity. This study focuses on bruise changes in dark-skinned individuals using tristimulus colorimetry for forensic analysis in such individuals. Methods Eighteen subjects of South Indian or Sri-Lankan ethnicity were recruited. Subjects were bruised using a vacuum pump and then daily colour measurements were taken of the bruise using a tristimulus colorimeter. The L* a* b* readings were recorded of a control area and of the bruise until it disappeared. Two Caucasians were used for comparison. Results This study showed that, using colorimetry, bruises on dark-skinned individuals can be measured and analysed even if the bruises are unclear visually. As the bruise is beneath the skin, the colour difference Δ L*, Δ a* and Δ b* were calculated. All values showed a trend, indicating that the L* a* b* measuring technique is a reliable method to analyse bruises on dark-skinned individuals. Comparisons of Asian subjects and Caucasian subjects were performed. The largest difference was seen in the b* value. Statistical analysis showed that Δ L* colour difference was the most consistent (95% CI −4.05 to −2.49) showing a significant difference between days 1–4 and 5–8. Conclusion Objective assessment of bruises on dark-skinned individuals using the L* a* b* method of measuring gave reproducible results. Furthermore, the study showed that the yellowing of a bruise cannot be seen or measured with a tristimulus colorimeter on dark-skinned individuals due to the pigmentation of the skin. With further studies and more subjects, the age of bruises could potentially be assessed for use in forensic analysis.