Differentiation of hair using ATR FT-IR spectroscopy: A statistical classification of dyed and non-dyed hairs

Abstract 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. In this study, non-dyed and dyed hairs from individuals varying in race, biological sex, and age, were analyzed using attenuated total reflection Fourier transform-infrared (ATR FT-IR) spectroscopy. Through the incorporation of multivariate statistical analysis, spectra collected from dyed and non-dyed hairs were differentiated with high accuracy. 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 here allowed for predicting whether an individual used a permanent hair dye, and then the brand and color of hair dye used, with at least 90% 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.

[1]  Kyle C. Doty,et al.  Forensic Hair Differentiation Using Attenuated Total Reflection Fourier Transform Infrared (ATR FT-IR) Spectroscopy , 2016, Applied spectroscopy.

[2]  M. Barker,et al.  Partial least squares for discrimination , 2003 .

[3]  R. V. Van Duyne,et al.  In situ detection and identification of hair dyes using surface-enhanced Raman spectroscopy (SERS). , 2015, Analytical chemistry.

[4]  Rekha Gautam,et al.  Review of multidimensional data processing approaches for Raman and infrared spectroscopy , 2015, EPJ Techniques and Instrumentation.

[5]  J. Bohan.  Review of: Strengthening Forensic Science in the United States: A Path Forward , 2010 .

[6]  M M Houck.  Forensic Human Hair Examination and Comparison in the 21st Century. , 2005, Forensic science review.

[7]  D. Ballabio,et al.  Classification tools in chemistry. Part 1: linear models. PLS-DA , 2013 .

[8]  Max M. Houck,et al.  The science of forensic hair comparisons and the admissibility of hair comparison evidence: Frye and Daubert considered. , 2004 .

[9]  R. Dhurat,et al.  Hair Evaluation Methods: Merits and Demerits , 2009, International journal of trichology.

[10]  Terry Melton.  Mitochondrial DNA Examination of Cold Case Crime Scene Hairs , 2006 .

[11]  C. el Rawadi,et al.  Diversity of hair growth profiles , 2005, International journal of dermatology.

[12]  Law. Policy.  Executive Summary of the National Academies of Science Reports, Strengthening Forensic Science in the United States: A Path Forward , 2009 .

[13]  G. J. Weston.  The infra-red spectrum of peracetic acid-treated wool. , 1955, Biochimica et biophysica acta.

[14]  Sarina Brandes.  Near-infrared spectroscopic studies of human scalp hair in a forensic context , 2009 .

[15]  J. Goodpaster,et al.  Forensic Discrimination of Dyed Hair Color: I. UV‐Visible Microspectrophotometry *† , 2010, Journal of forensic sciences.

[16]  Robert Ogle,et al.  Atlas of Human Hair: Microscopic Characteristics , 1998 .

[17]  Serge Kokot,et al.  Matching and discrimination of single human-scalp hairs by FT-IR micro-spectroscopy and chemometrics , 1999 .

[18]  Helen Panayiotou,et al.  Vibrational spectroscopy of keratin fibres : A forensic approach , 2004 .

[19]  O. Morel,et al.  Current trends in the chemistry of permanent hair dyeing. , 2011, Chemical reviews.

[20]  E. F. Pearson.  Forensic Science Handbook , 1983 .

[21]  R A Wickenheiser,et al.  Further evaluation of probabilities in human scalp hair comparisons. , 1990, Journal of forensic sciences.

[22]  J. Goodpaster,et al.  Forensic Discrimination of Dyed Hair Color: II. Multivariate Statistical Analysis *,† , 2011, Journal of forensic sciences.

[23]  P. M. Barton.  A forensic investigation of single human hair fibres using FTIR-ATR spectroscopy and chemometrics , 2011 .

[24]  J. Guthrie,et al.  The characterisation of treated and dyed hair , 1995 .

[25]  R. Brereton,et al.  Partial least squares discriminant analysis: taking the magic away , 2014 .

[26]  Jessica Brand,et al.  It is Now Up to the Courts: "Forensic Science in Criminal Courts: Ensuring Scientific Validity of Feature-Comparison Methods" , 2017 .

[27]  F. J. Holler,et al.  Principles of Instrumental Analysis , 1973 .