Analyses

The proper recognition and collection of paint evidence at the scene precedes the comparison of evidence occurring at the laboratory. The color, texture, type, layer sequence, and chemical composition of known and questioned paints are compared, and a conclusion is rendered. Additionally, in cases for which no suspect vehicle and questioned paint are available, it may be possible to provide at least an investigative lead based on the color and metallic/nonmetallic type of paint present. If appropriate, the Royal Canadian Mounted Police’s PDQ (Paint Data Query) database may be searched, and vehicular information may be provided regarding the possible makes, models, and year range of vehicles that used the questioned paint system.

The examination and comparison of paint evidence requires microscopic and instrumental techniques and methods. The examination of questioned and known samples follows an analytical process that identifies and compares the class (or group) characteristics of the evidence.100 Occasionally, identifying characteristics exist across edges that allow edge or piece fitting. These characteristics include irregular borders, brush stroke striations, polish mark striations, or surface abrasion markings. When paint fragments physically fit back to a sample from a known source, the fragments are identified as having come from that specific source. Only when physical fitting is possible can an individualized source determination be made

Examiners involved with the analysis of paint evidence in the laboratory typically possess an extensive scientific background, because many of the methods and analyses rely heavily on chemistry.101 The suggested minimum education requirement is a bachelor’s degree in a natural102,103 or applied science,104 with many candidates possessing a graduate degree. Coursework needs to include one year (or equivalent) of general chemistry with laboratory, organic chemistry with laboratory, analytical/instrumental analysis, and light microscopy to include basic polarized light microscopy—the latter obtained through structured coursework if it is not available at the graduate or undergraduate level.105 On-the-job training continues in the laboratory, with its length depending on the examiner’s experience. Before examiner trainees can work cases independently, they must observe and

100

SWGMAT. 1999. Forensic paint analysis and comparison guidelines. Forensic Science Communications 1(2). Available at www.fbi.gov/hq/lab/fsc/backissu/july1999/painta.htm.

101

SWGMAT. 2000. Trace evidence quality assurance guidelines. Forensic Science Communications 2(1). Available at www.fbi.gov/hq/lab/fsc/backissu/jan2000/swgmat.htm.

102

G.S. Anderson (ed.). Canadian Society of Forensic Science. 2007. CSFS Careers in Forensic Science, p. 15. Available at www.csfs.ca/contentadmin/UserFiles/File/Booklet2007.pdf.

103

SWGMAT 2000, op. cit.

104

Ibid.

105

Ibid.



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