New perspectives in the use of ink evidence in forensic science: Part I. Development of a quality assurance process for forensic ink analysis by HPTLC

Abstract The level of information provided by ink evidence to the criminal and civil justice system is limited. The limitations arise from the weakness of the interpretative framework currently used, as proposed in the ASTM 1422-05 and 1789-04 on ink analysis. It is proposed to use the likelihood ra...

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Bibliographic Details
Published in:Forensic science international 2009-03, Vol.185 (1), p.29-37
Main Authors: Neumann, Cedric, Margot, Pierre
Format: Article
Language:English
Subjects:
Biological and medical sciences
Calibration
Digital capture
Forensic medicine
Forensic sciences
General aspects
Ink
Interpretation
Investigative techniques, diagnostic techniques (general aspects)
Libraries
Manufacturers
Medical sciences
Pathology
Pens & pencils
Public health. Hygiene
Public health. Hygiene-occupational medicine
Standardisation
Statistics
Writing
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Summary:Abstract The level of information provided by ink evidence to the criminal and civil justice system is limited. The limitations arise from the weakness of the interpretative framework currently used, as proposed in the ASTM 1422-05 and 1789-04 on ink analysis. It is proposed to use the likelihood ratio from the Bayes theorem to interpret ink evidence. Unfortunately, when considering the analytical practices, as defined in the ASTM standards on ink analysis, it appears that current ink analytical practices do not allow for the level of reproducibility and accuracy required by a probabilistic framework. Such framework relies on the evaluation of the statistics of the ink characteristics using an ink reference database and the objective measurement of similarities between ink samples. A complete research programme was designed to (a) develop a standard methodology for analysing ink samples in a more reproducible way, (b) comparing automatically and objectively ink samples and (c) evaluate the proposed methodology in a forensic context. This report focuses on the first of the three stages. A calibration process, based on a standard dye ladder, is proposed to improve the reproducibility of ink analysis by HPTLC, when these inks are analysed at different times and/or by different examiners. The impact of this process on the variability between the repetitive analyses of ink samples in various conditions is studied. The results show significant improvements in the reproducibility of ink analysis compared to traditional calibration methods.
ISSN:0379-0738
1872-6283
DOI:10.1016/j.forsciint.2008.11.016