NCJ Number
221351
Date Published
2007
Length
20 pages
Annotation
This report presents the FBI Scientific Working Group for Materials Analysis' guideline for color analysis of commercially prepared paints and coating.
Abstract
The guideline is intended to assist individuals and laboratories in conducting forensic visible and ultraviolet (UV) spectral analyses on small fragments of paint. It is designed to assist an analyst in the selection of appropriate sample-preparation methods and instrumental parameters for the analysis, comparison, or identification of paint pigments and colors. The guideline does not intend to present comprehensive theories and methods of microspectrophotometry. The analyst is presumed to have an understanding of UV-visible microspectrophotometry and the general concepts of specimen preparation. Regarding analytical procedures, the guideline provides guidance on the handling of reflectance test specimens and transmission test specimens. A general recommendation is that at least 5 spectra be collected from each noneffect paint film and up to 10 spectra for effect finishes, each representing different areas of the sample, in order to demonstrate the range of variation in a paint sample. The guideline also contains recommended procedures for instrument calibration, instrument setup and scanning parameters, and spectral comparison and interpretation. The latter includes a statement of fundamental steps of comparison and interpretation. In addition, the guideline recommends procedures for colorimetry value comparison and interpretation, the statement of conclusions, and procedures for comparing samples measured with microspectrophotometers with a database compiled using commercial or industrial instruments. Also discussed are what should be included in case notes (documentation). 15 references