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The effects of sun exposure on colorant identification of permanently and semi-permanently dyed hair

NCJ Number
Scientific Reports Volume: 13 Issue: 2168 Dated: 7 February 2023
Date Published
February 2023
6 pages

The authors hypothesized and tested that confirmatory analysis of hair colorants can be used to facilitate and advance forensic analysis of human remains.


During bloating and active decay, human remains begin to deform and warp their physical identity. After the skin and muscles loosen and detach from their skeletal structuration, everything but bones, teeth, and hair will fully disintegrate into the soil that surrounds the body. Nearly half of people in the world dye their hair with a variety of permanent and semi-permanent colorants. A growing body of evidence suggests that hair colorants can be identified directly on hair using surface-enhanced Raman spectroscopy (SERS). In this study, the authors investigate the extent to which SERS can be used to detect black and blue permanent and semi-permanent dyes on hair exposed to sunlight. Their results showed that although substantial photodegradation of all dyes was observed by week 7, SERS enabled highly accurate detection and identification of hair colorants during all 10 weeks of hair exposure to the sunlight with on average 99.2% accuracy. The authors also found that SERS could be used to predict fading rates of hair colorants. This information can shed light on the exposure of human remains to the exterior environment. (Published abstract provided)

Date Published: February 1, 2023