Metals Flashcards
1
Q
Where is metal found as trace evidence?
A
- 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
2
Q
What are the orimary techniques used to analyse metal trace evidence?
A
- SEM-EDX
- XRF
- XRD
- HPLC
- GC-MS
- AAS
- LA-ICP-MS
- colour spot and presumptive chemical tests
3
Q
What is inorganic GSR from?
A
- primer mixture
- cartridge case
4
Q
What is organic GSR from?
A
- smokeless powder
- primary explosives
- stabilisers
- platicisers
- sensitisers
- flash inhibitors
- combustion products also found on spent cartridge and muzzle
5
Q
What are the four categories of detection of GSR?
A
- 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
6
Q
How do you detect metals in latent fingermarks?
A
- XRF-microscopy
- identify differences between handling gun barrel and ammunition cartridge above background activity
7
Q
How do you detect explosive trace evidence?
A
- 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
8
Q
What combination of trace evidence types is fireworks?
A
- paper
- plastic
- explosives
- metal
