Detection and identification of hair dyes directly at a crime scene by surface-enhanced Raman spectroscopy (SERS)

Hair is one of the most common types of physical evidence found at a crime scene. Forensic examination may suggest a connection between a suspect and a crime scene or a victim, or demonstrate an absence of such associations. Therefore, forensic analysis of hair evidence is invaluable to criminal investigations. Current hair forensic examinations are primarily based on a subjective microscopic comparison of hair found at the crime scene with a sample of suspect’s hair. Since this is often inconclusive, development of alternative and more accurate hair analysis techniques are critical. We propose to develop the use of Surface-Enhanced Raman Spectroscopy (SERS) for label-free, non-invasive, non-destructive and confirmatory detection and identification of artificial dyes directly on hair. Our preliminary results show that SERS is capable of identifying whether the hair is dyed or not, distinguish between permanent and semipermanent dyes, as well as different commercial brands of colorants directly on hair. Expanding upon this discovery, we propose to develop the use of SERS for (1) identification whether hair is re-dyed by synthetic permanent, semi-permanent or natural dyes, (2) determination of how many dyes are simultaneously present on hair and (3) what colorant was applied first and what colorant was used to re-dye hair. We will also build spectroscopic library of dyes that can be used to (4) distinguish between commercial brands of colorants. The spectroscopic library will be available for forensic experts in the U.S. Lastly, we propose to (4) develop a SERS Kit that will enable confirmatory on-site SERS analysis of hair.