Comparative Analysis of Car Paint Traces in Terms of Color by VIS Microspectrometry for Forensic Needs

Abstract

The usefulness of VIS microspectrometry for comparison of very small car paint traces was studied. Eighteen samples of solid and metallic paints taken from new and repainted cars were examined. Each sample was measured in both transmittance and reflectance mode (on top surface and on cross-section). Using the CIELAB units the repeatability of the color measurement was assessed. A criterion allowing two parts of the same sample and two samples of the same color to be distinguished was established. The method was proved to be an useful instrumental tool-complementary to other analytical methods (e.g., IR spectrometry)-in examination of car paint traces for forensic purposes.

Evaluation of evidence value of car primer using pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) and chemometrics

“…The ∆E value obtained for red basecoats is shown in Table 3. Zieba-Palus [21] stated that the two colours were different from each other if the ∆E value is larger than 10. The ∆E value obtained by most of the red basecoats was larger than 10 except for sample differentiation between red basecoat A-C, A-G, B-F, and C-G.…”

Quantification of vehicle paint components containing polystyrene using pyrolysis-gas chromatography/mass spectrometry

“…E-mail: gaston@emome.net; Fax: +886 2 22392404; Tel: +886 2 29332901 sample quality to rigorous pretreatment procedures. 3 That is, precautions should be carefully taken when a great similarity of colors is confirmed, even if some differences were obtained by IR.…”

Appearance and Spectroscopic Characterization of Automotive Coatings for Forensic Purposes

“…26 A group at the Institute of Forensic Research in Krakow have obtained CIELAB coordinates from their spectra of non-neutral automotive base coats, and used the color difference formula to gauge the sensitivity of the method for discriminating similar samples and replicates of the same sample. 18,19,28 This group found most significant differences in transmission spectra between similar colored paints. Forensic examinations should require R-MSP measurements to compare with color meter measurements, as well as T-MSP measurements for analysis of significant spectral differences.…”

“…17 The simplest CIE color difference formula is shown in Equation 1, and is most commonly used in the current literature to represent the color difference between two automotive coatings. [18][19][20] However, visual discrimination of similar colors differs by hue, with non- (1)…”

“…T-MSP is typically performed on cross sections prepared by microtomy; this can be significantly more time-consuming and require additional training. 18,19 However, studies employing all three techniques on the same samples have found transmission spectra are more varied than reflectance spectra, and may permit differentiation between extremely similar, but different samples more effectively than only reflectance mode. The authors of these studies recommend use of transmission in conjunction with at least one reflectance technique.…”