Application of dye analysis in forensic fibre and textile examination: Case examples

- Application of dye analysis by HPLC-DAD-MS shown in seven cases and a qualtiy assurance test.
- Dye analyses requires only minute samples and can be applied to several types of fibres, e.g. cotton, polyester, polyamide.
- Dye analyses indicate that dye mixtures are common. This improves the evidential value that can be obtained.
- Dyes in complex dye mixtures can be identified independently.
- Dye analyses allows comparison of samples that have been altered, e.g. by heat or are very heterogeneous.

Seven cases and a quality assurance test are presented. In these cases, fibres or textiles submitted for investigation were analysed by HPLC-DAD-MS to identify the dyes present. The cases presented illustrate that it is possible to identify textile dyes in fibre traces recovered for forensic analysis. The results show that a mixture of dyes is present in all textiles investigated, except one sample that was taken from a manufacturer dye shade card. It is concluded that dye analyses improves the evidential value of forensic fibre examinations, as it becomes possible to distinguish textiles that are different in dye chemistry, but have a similar colour. In addition dye analysis makes the examination more robust, as it becomes possible to attribute colour differences between samples to identical dyes (mixed in different ratios) or to chemically different dyes.