Swaraldahab, M. A. H., & Christensen, A. M. (2016). The effect of time on bone fluorescence: Implications for using alternate light sources to search for skeletal remains. Journal of Forensic Sciences, 61(2), 442–444.

This 2016 study by Swaraldahab and Christensen evaluated how the passage of time impacts the intensity of bone fluorescence, a property driven by organic collagen proteins (specifically the natural fluorophores tyrosine and tryptophan) that degrade and denature over time. To analyze this relationship, the researchers examined skeletal specimens from four distinct temporal groups ranging from 0 to 1064 years old—recent (domestic pig), semi-recent (macerated pig), historic (human skeletal collection), and ancient (human archaeological remains)—by photographing them under a 490 nm wavelength (blue light) alternate light source (ALS) with an orange camera filter. The results revealed a significant inverse correlation (\(r = -0.6, R^2 = 0.324\)) between bone age and fluorescence intensity, showing a steady decline in mean grayscale brightness from recent samples (169.31) down to ancient samples (89.17) compared to a negative control benchmark of 85. Ultimately, the study concludes that while regular fluorescence cannot be routinely expected beyond roughly 200 years, older samples do retain some trace fluorescent properties, confirming that ALS screening remains a highly reliable and budget-friendly tool for standard modern forensic cases which typically fall under 50 years of age.

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