Collection and Polarized Light Microscopy Analysis of Textile Fiber Evidence in Traffic Accidents

• Main Authors: Yueh-Hsiang Chen, 陳躍翔
• Other Authors: Yung-Fou Chen
• Format: Others
• Language: en_US
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/h82xhk

碩士 === 中央警察大學 === 鑑識科學研究所 === 99 === Crime scene investigators collect and preserve evidences in major criminal cases, except for homicide, robbery, and sexual assault cases attracting public attention, also playing important roles in traffic accidents investigation, especially in traffic homicide cases. To effectively collect accident evidence, investigators must thoroughly understand the dynamic relationships from pre-accident to post-accident between the vehicle and the victim, vehicle damage, evidence left patterns and locations, victim’s traumatic injuries, and clothes abrasions and lacerations. In this study, 22 cases were studied to get a better strategy for forensic traffic accident textile fiber evidence search and collection. Traffic accidents involved pedestrians and scooter riders can be classified into 4 categories. Forensic fiber analysis by polarized light microscopy (PLM) usually re-fers to observation refractive index, extinction, interference colors, birefringence and other physical properties under the polarized light micro-scope to determine fiber generic types. In this study, retardations of textile fiber specimens were measured with Berek compensator under the polarized light microscope. This method improves the accuracy and digitalizes the result of interference colors observation with true retardation. A datasheet for forensic textile fiber identification with polarized light microscopy is proposed, and the flowchart system is theorized. The datasheet and flowchart system allow forensic textile fiber examiners to distinguish and identify common synthetic fibers encountered in caseworks.