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Differentiation of Hair Using ATR FT-IR Spectroscopy: A Statistical Classification of Dyed and Non-dyed Hairs

NCJ Number
Date Published
December 2017
9 pages
This study analyzed non-dyed and dyed hairs from individuals varying in race, biological sex, and age, using attenuated total reflection Fourier transform-infrared (ATR FT-IR) spectroscopy.
Although hair is one of the most common and abundant types of evidence found at a crime scene, the current forensic analyses employed underutilize its full potential evidentiary value. Microscopy is the fundamental technique used to analyze forensic hair evidence, but even this routine and well-accepted method has limitations. The current study incorporated multivariate statistical analysis in differentiating with high accuracy spectra collected from dyed and non-dyed hairs. After hair spectra were determined to be dyed or non-dyed, dyed hair spectra were successfully differentiated among themselves based on brand (or manufacturer) and dye color. The methodology developed enables the prediction of whether an individual used a permanent hair dye, and then the brand and color of hair dye used, with at least 90 percent confidence. The high accuracy shown in this study illustrates the ease and robustness of coupling ATR FT-IR spectroscopy and multivariate statistics for forensic hair analysis, specifically for the analysis of hairs dyed with dark colored hair dyes. The use of spectroscopy for forensic hair analysis, as demonstrated by this initial proof of concept study, would advance the field of trace evidence as a whole, and can potentially be utilized to confirm conclusions drawn from methodologies employed currently, in turn leading towards increased individualization. (publisher abstract modified)

Date Published: December 1, 2017