Visibility of inflicted bruises by alternate light: Results of a randomized controlled trial

Abstract

Difficulty visualizing bruises resulting from interpersonal violence, especially in individuals with dark skin, contributes to disparities in access to justice. The purpose of this analysis was to compare bruise visibility of detected injuries using white light versus alternate light sources (ALS). Visibility was assessed using the 5-point Bruise Visibility Scale (BVS) for white light and the ALS Visibility Scale (AVS) for ALS. Bruises were induced using controlled application of a paintball to the upper arm on 157 healthy adults across six skin color categories. Using a crossover design, the light source used first to assess the bruise (white light or ALS) was randomized. Each bruise was examined up to 21 times over 4 weeks using white light and 10 combinations of wavelengths (350 nanometer [nm] - 535 nm) and colored filters (yellow, orange, and red). Multilevel modeling was used to analyze the repeated measures data with a total 20,103 bruise assessments. Results revealed 415 nm with yellow filter resulted in an almost 0.5-point increase in BVS/AVS score across all skin colors (Estimate = 0.46; 95% CI: 0.43, 0.49; p < 0.001), a clinically significant improvement in ability to visualize bruises. Conversely, 515 nm (Estimate = -0.80; 95% CI: -0.84, -0.76; p < 0.001) and 535 nm (Estimate = -0.64, 95% CI: -0.67, -0.60; p < 0.001) with red filter resulted in more than 0.5-point decrease in BVS/AVS score. The use of ALS is supported by the data and results in improved bruise visibility during medical forensic examinations.

Keywords: alternate light; bruises; detection; forensic examination; forensic light; injury; ultraviolet; violence.