Fibres & Textiles PDF Forensic Science Lecture Notes

Fibres & Textiles LEC04 – Monday September 16th FRSC2030H Foundations in Forensic Science  LAB01 Continues ODD Sections Post-lab Assignment Course Update LAB02 Next week Outdoor Lab Interpol Internation Criminal Police Organi...

Fibres & Textiles LEC04 – Monday September 16th FRSC2030H Foundations in Forensic Science  LAB01 Continues ODD Sections Post-lab Assignment Course Update LAB02 Next week Outdoor Lab Interpol Internation Criminal Police Organization Lyon, France Established in 1923 WWII Reestablished in 1946 196 Members Role 1. assistance between police authorities 2. Establish institutions to prevent & suppress Fibre Evidence Natural Fibres derived entirely from animal or plant sources wool, cashmere, cotton, etc. Ribbonlike shape with twists at irregular intervals Manufactured Fibres derived from either natural or synthetic polymers Rayon, Polyester, Nylon, Spandex, etc. Very uniform, flexible, strong Trace Evidence “trace” Colloquial: (adjective) the small size of materials Forensics: traces at the crime scene are not restricted to a small size “interrogatable traces” Develop an understanding of physical details of an event “associative traces” Source attribution Case Study – Vehicular Murder 47-year old man found dead Empty overturned vehicle found 20m away Stolen Break marks present Son reports the crime Lost control Dragged father out Left the scene Case Study – Vehicular Murder Autopsy findings Large number of injuries Excoriations Displaced upper third for both legs ‘contusive’ forces Consistent with road traffic accidents Autopsy compatible with Son’s story Vehicle examined Small fragment of grey fibres found on damaged front light Could not be excluded from deceased jacket “…the small textile fibres on the front lights of the car supported only one explanation and decisively contributed to distinguishing between the hitting of a pedestrian and injuries sustained after a car accident.” Case Study – Murder of David Watkins Jan. 1993 Man found shot & killed Andrew Emerson arrested (10 days later) Feb. 1994 Acquitted for murder of D. Watkins Case relied on only fibre evidence 39 fibres Peugeot 309 GTi vs. Peageot 205 GTi “A total of 39 fibres of three different types have been found on the clothing of David Watkins that could have come from the seats of the Peugeot 309 GTi or [Mr. F’s] Peugeot 205 GTI. However, given that David Watkins had not been in [Mr. F’s] car for more than a month before his death, these fibres provide strong evidence to indicate that David Watkins had recently sat in Andrew Everson's car.” Case Study – Murder of David Watkins Case Study – Murder of David Watkins Case Study – Murder of David Watkins Re-trial Relabeling each fibre uniquely Examining lifts from suspects vehicle Comparisons to fibres found on victim Exclusion of friend’s vehicle Identification of relevant fibre populations “the findings provide extremely strong scientific support for the proposition that the clothing worn by David Watkins was in recent, direct contact with the interior of the vehicle owned by Andrew Everson” Collection & Instrumentation Fibre Collection Tape Lifts Many studies comparing different tapes Different storage techniques Non-invasive techniques Examination of microplastic shedding Issues: Standards Training SOPs Instrumental Methods Automated Fibre Search SHUTTLE project Microscopy Standard for examination of fibre evidence Comparison of USB microscopes Confocal Microscopy Used to examine morphology of fibres Microspectrophotometry (UV-VIS) Compares visible colour from samples Colourless fibres Instrumental Methods Raman Dyes Laser used onto sample Vibrations measured Infrared Spectroscopy Dyes & polymer analysis Light onto sample Absorbtion, frequency, wavelength measured Chromatography Column with solvent Mobile and stationary phase Gas/Liquid chromatography Damage analysis Textile Damage PCAST report (2016) Need for clarity Validity and reliability of forensic methods Impact of cognitive bias Requirements of training Knowledge of the fabrics, yarns and fibres Australia & New Zealand Textile Damage Working Group (TDWG) Textile Damage Aliverdipour et al. Fabric tensile behaviour vs penetrative resistance Tested 3 knives & 2 spikes On materials: shirting fabric, worsted, elastic denim, artificial leather and tarpaulin Two factors: geometrical characteristics & tensile strength of the fabrics Greater tip angle of sharp object = higher penetrative force Nichols-Drew et al. Tested rounded tipped knives On material: cotton, demin, synthetic, faux leather “a knife with a good rounded tip has the least chance to penetrate a fabric” Textile Damage Li et al. Examined HMWPE garments Greater thickness HMWPE-based fabric has impact on stab resistance Angel also has impact: 90◦ has greatest resistance Other findings Metal threads increase resistance Weave pattern Fabric density Stabbing simulations Skin and skin simulants Fibre Damage Fibre Damage Machnowski et al. – Heat Cotton vs polyester Scanning electron microscope & FTIR Porosity of fabric DeBattista et al. – Light Wool & cotton photodegradation Fading is variable & unpredictable Mujumdar et al. – Weathering conditions Desert (Arizona) vs Humid (Florioda) for 12 months Able to discriminate between treatments & time periods Acrylic fibres harder to discriminate Fibre Damage Dolan et al. – Oil-and-water-repellent fabrics 12 weeks outdoor exposure & 10 launders 95.5% detection thru Gas Chromatography Ueland et al. – Decomp fluid on clothing “cotton t-shirt, polyester briefs and polyester- cotton socks” Buried pig carcasses for 1, 3, 6, 9, 12, 18 and 24 months Cotton disintegrated after 12 months Decomp fluids improved preservation of textiles Especially for cotton Forensic Research Data from Forensic Research Expert: Fibre databases Population studies Transfer & persistence probability research Run simulations with materials Databases No ideal database Muehletahler et al. Web-crawling to pull fibre information Cotton most abundant (80%) Most common colours: white, black, & blue Data from Forensic Research Cadola et al. – Canada Database literature transfer, persistence and population studies DNA, hairs, fibres, etc. Search based on type of trace, year, type of study Sneath et al. – Transfer of fibres after stabbing Textile construction Cotton short and non elastic, therefore sheds more Skokan et al. – Fibre transfer mechanism Fiber type, morphology and size Cotton most sheddable Prinsen et al. – Smothering of Dummy 181 music festival visitors Knots & Rope Analysis Knots & Rope Analysis Mostly common knots used 5% used skilled/trained Drawing & reconstructing Sinuosity Knot damage Suicide vs murder Chirality Looseness & access Case Study – Italy 2020 72-year-old man found floating Slipknot around neck with 3 loops at other end Bruising around throat Autopsy Injuries Froth & water in airways Cause of death Asphyxia resulting from strangulation & drowning Stones found on seabed Summary Double relevant research topics from previous years Development of databases Standards & best practices European Textile & Hair Group (2019) Damage to fibre & textiles New fibres still emerging Population trends