Discrimination of automotive window tint using ATR-FTIR spectroscopy and chemometrics

Braden Grant; Georgina Sauzier; Simon W Lewis

doi:10.1016/j.forsciint.2020.110338

Discrimination of automotive window tint using ATR-FTIR spectroscopy and chemometrics

Forensic Sci Int. 2020 Aug:313:110338. doi: 10.1016/j.forsciint.2020.110338. Epub 2020 May 16.

Authors

Braden Grant¹, Georgina Sauzier², Simon W Lewis³

Affiliations

¹ School of Molecular and Life Sciences, Curtin University, GPO Box U1987, Perth, WA 6845, Australia. Electronic address: Braden.Grant@graduate.curtin.edu.au.
² School of Molecular and Life Sciences, Curtin University, GPO Box U1987, Perth, WA 6845, Australia; Curtin Institute of Functional Molecules and Interfaces, Curtin University, GPO Box U1987, Perth, WA 6845, Australia. Electronic address: Georgina.Sauzier@curtin.edu.au.
³ School of Molecular and Life Sciences, Curtin University, GPO Box U1987, Perth, WA 6845, Australia; Curtin Institute of Functional Molecules and Interfaces, Curtin University, GPO Box U1987, Perth, WA 6845, Australia. Electronic address: S.Lewis@curtin.edu.au.

PMID: 32497994
DOI: 10.1016/j.forsciint.2020.110338

Abstract

Automotive window tints are commonly applied to motor vehicles to reduce transmittance of light and heat into the interior. They may hence be encountered as physical evidence in criminal investigations, or in civil matters where a tint is suspected to originate from a different source than advertised. Establishing a tint's provenance would be highly relevant in such cases. However, there are currently a lack of established guidelines for forensic tint analysis. This study used attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy with chemometrics to characterize automotive tints based on their adhesive composition. Minimal variability was observed within a single roll of tint, however substantial variability was observed between tints of different brands. Certain individual tint products were also found to possess highly distinctive spectra. Subsequent predictive models were able to associate unknown tint samples to their brand, and found to be robust to both adhesive curing and short-term environmental exposure over a five-month period. The use of ATR-FTIR spectroscopy and chemometrics thus offers a rapid and objective approach to discriminating automotive tints for forensic purposes.

Keywords: Automotive; Chemometrics; Forensic; Infrared spectroscopy; Polymer.