Bruise identification and age estimation – Review on challenges and emerging visualization techniques

Abstract: Bruise color has traditionally been used to infer injury age, yet multiple studies show that gross visual inspection is highly unreliable, particularly in individuals having darker skin complexion. This narrative review examines the limitations of visual color assessment for bruise age estimation and synthesizes emerging evidence on photographic, colorimetric, spectrophotometric, multispectral, and alternate light source (ALS) techniques, with emphasis on their performance across different skin complexions. A structured search of PubMed and other databases identified key clinical and experimental studies, including work on tristimulus colorimetry and reflectance spectrophotometry, ALS and multispectral imaging for bruise detection, and infrared photography in blunt force trauma documentation. The evidence consistently demonstrates large inter- and intra-observer variability in visual color description and poor accuracy of color-based ageing, while objective methods can model systematic changes in bruise color over time but remain strongly influenced by skin tone, bruise size, and imaging modality. ALS at violet–blue wavelengths with appropriate filters improves bruise visibility, especially on darker skin, whereas cross-polarized photography, color scales (e.g., NNDV), and colorimetry enhance documentation and quantification rather than providing precise age cutoffs. Current data support abandoning rigid visual color timetables in favor of standardized imaging and quantitative approaches, and highlight the urgent need for validation of these techniques in diverse populations, including Indian skin types, before they can be relied upon for forensic bruise dating in practice.