Metals
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Where is metal found as trace evidence?
• rust and metal shavings transferred to a person or clothing • metal weapon used in an assault leaving trace in the wound • gunshot residue • fireworks & sparklers • metal filings on a pipe wrench after a twist attack on a doorknob • metal from a crowbar used to force open a window or door • explosive residue • lightbulb filaments
What are the orimary techniques used to analyse metal trace evidence?
• SEM-EDX • XRF • XRD • HPLC • GC-MS • AAS • LA-ICP-MS • colour spot and presumptive chemical tests
What is inorganic GSR from?
• primer mixture • cartridge case
What is organic GSR from?
• smokeless powder • primary explosives • stabilisers • platicisers • sensitisers • flash inhibitors • combustion products also found on spent cartridge and muzzle
What are the four categories of detection of GSR?
• optical methods - organic compounds have strong IR-luminescence, non-destuctive, fast, low specificity, high LOD • chemographic testing - invasive, can be performed at crimescene, inorganic elements with presumptive testing, high selectivity, only qualitative, risk of false positives • spectrometry - inorganic compounds, SEM-EDX (quantitative), takes time, highest compositional and morphological detail • separation methods - coupled with MS (LC/GC-MS/MS), invasive, reliable, low LOD
How do you detect metals in latent fingermarks?
• XRF-microscopy • identify differences between handling gun barrel and ammunition cartridge above background activity
How do you detect explosive trace evidence?
• ion mobility spectroscopy • separates and identifies ionised molecules present in the gas phase based on their mobility in a carrier buffer gas • controlled ionisation and separation • fast measurments
What combination of trace evidence types is fireworks?
• paper • plastic • explosives • metal