Enhancing the evidential value of textile fibres Part 2: Application of a database-driven fibre comparison strategy to a cold-case investigation.

This paper describes the involvement of our laboratory in a Western Australian 'cold-case' investigation that spanned 24 years. The investigation was widely considered to be the largest in Australian history. During the investigative phase, our laboratory was tasked with the collection of trace evidence of all types in connection with a sexual assault and two homicides that were suspected to be related. Textile fibres represented the vast majority of trace evidence recovered. A much greater quantity of fibres (>10,800) was collected than would be typical for a routine case, as fibres of any colour or type were potentially of investigative value. The investigation was unprecedented in its scale, and presented numerous challenges in terms of evidence recovery, analysis, interpretation, reporting, and provision of testimony. A textile fibre microspectrophotometric (MSP) database was developed specifically for the interpretation of data in connection with the investigation. The database currently contains over 25,000 normalised and first derivative spectra of casework, validation and reference textile fibres. A fibre comparison strategy was devised, involving the identification of preliminary fibre groups on the basis of corresponding/similar MSP spectra, and verification of these groups via brightfield and fluorescence comparison microscopy. A potential link to an automotive source was identified for one of the homicide victims during the investigative phase. After identification of a suspect, a total of 98 fibres recovered from victims and from a seized motor vehicle were found to correspond in properties to six different fibre types from known textile sources in connection with the suspect. A highly publicised criminal trial was held, and textile fibre evidence provided a major contribution to the trial findings, in which the accused was found guilty of two homicides.