Direct Analysis of Human Hair Before and After Cosmetic Modification Using a Recent Data Fusion Method

Mônica Santos,Fabíola Pereira

doi:10.21577/0103-5053.20190121

Mônica Santos, Fabíola Pereira

Open Access

https://doi.org/10.21577/0103-5053.20190121

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Abstract

The cosmetic modification of hair is a very common procedure used to mask or cover evidence at a crime scene. Deoxyribonucleic acid (DNA) tests are expensive and require good-quality collection of samples and a database profile. To overcome these challenges, direct analysis was performed on a large set of hair strands collected from individuals, denoted original samples, and the data were compared with those of the same samples after cosmetic modification performed by bleaching the samples in the laboratory. A total of 127 samples were evaluated in this study using two analytical techniques, wavelength-dispersive X-ray fluorescence (WDXRF) and laser-induced breakdown spectroscopy (LIBS). Instead of testing many algorithms to develop classification models for the original and bleached samples, a recent method was applied that combines information from 17 classifiers. Data fusion was also evaluated to improve the accuracy of the classification model, which was higher than 99.2%, with no requirements to select eigenvectors or thresholds.

Highlights

Human hair has macroscopic peculiarities, e.g., color and shape,[1,2] and the main molecular approach for hair characterization is deoxyribonucleic acid (DNA) sequencing,[3] which yields a unique fingerprint that differentiates one person from another
Principal component analysis (PCA) combined with the wavelength-dispersive X-ray fluorescence (WDXRF) spectra revealed that the chemical elements Cu and Fe were correlated with hair samples that had been straightened or dyed or with a single strand that had undergone both cosmetic procedures
Note that one original sample was found to be part of the bleached cluster. The issue with this sample was that compared to the other samples, the hair was gray in color with a different texture

Summary

Introduction

Human hair has macroscopic peculiarities, e.g., color and shape,[1,2] and the main molecular approach for hair characterization is deoxyribonucleic acid (DNA) sequencing,[3] which yields a unique fingerprint that differentiates one person from another. In our previous study,[13] we obtained good performance of a noninvasive method using wavelength-dispersive X-ray fluorescence (WDXRF) and pellets of strands of human hair without using chemicals or agglutinants.

Results

Conclusion