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Forensic determination of hair deposition time in crime scenes using electron paramagnetic resonance*†.

Authors
  • Shankar, Nikhita1
  • Guimarães, André O1, 2
  • Napoli, Eleonora1
  • Giulivi, Cecilia1, 3
  • 1 Department of Molecular Biosciences, School of Veterinary Medicine, University of California Davis, Davis, CA, USA.
  • 2 Laboratório de Ciências Físicas, Universidade Estadual do Norte Fluminense, Campos dos Goytacazes, RJ, Brazil. , (Brazil)
  • 3 MIND Institute, University of California Davis Medical Center, Sacramento, CA, USA.
Type
Published Article
Journal
Journal of forensic sciences
Publication Date
Sep 28, 2020
Identifiers
DOI: 10.1111/1556-4029.14570
PMID: 32986869
Source
Medline
Language
English
License
Unknown

Abstract

Several types of biological samples, including hair strands, are found at crime scenes. Apart from the identification of the value and the contributor of the probative evidence, it is important to prove that the time of shedding of hair belonging to a suspect or victim matches the crime window. To this end, to estimate the ex vivo aging of hair, we evaluated time-dependent changes in melanin-derived free radicals in blond, brown, and black hairs by using electron paramagnetic resonance spectroscopy (EPR). Hair strands aged under controlled conditions (humidity 40%, temperature 20-22°C, indirect light, with 12/12 hour of light/darkness cycles) showed a time-dependent decay of melanin-derived radicals. The half-life of eumelanin-derived radicals in hair under our experimental settings was estimated at 22 ± 2 days whereas that of pheomelanin was about 2 days suggesting better stabilization of unpaired electrons by eumelanin. Taken together, this study provides a reference for future forensic studies on determination of degradation of shed hair in a crime scene by following eumelanin radicals by utilizing the non-invasive, non-destructive, and highly specific EPR technique. © 2020 American Academy of Forensic Sciences.

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