Metals

Question 1

Where is metal found as trace evidence?

Answer 1

• 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

Question 2

What are the orimary techniques used to analyse metal trace evidence?

Answer 2

• SEM-EDX
• XRF
• XRD
• HPLC
• GC-MS
• AAS
• LA-ICP-MS
• colour spot and presumptive chemical tests

Question 3

What is inorganic GSR from?

Answer 3

• primer mixture
• cartridge case

Question 4

What is organic GSR from?

Answer 4

• smokeless powder
• primary explosives
• stabilisers
• platicisers
• sensitisers
• flash inhibitors
• combustion products also found on spent cartridge and muzzle

Question 5

What are the four categories of detection of GSR?

Answer 5

• 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

Question 6

How do you detect metals in latent fingermarks?

Answer 6

• XRF-microscopy
• identify differences between handling gun barrel and ammunition cartridge above background activity

Question 7

How do you detect explosive trace evidence?

Answer 7

• 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

Question 8

What combination of trace evidence types is fireworks?

Answer 8

• paper
• plastic
• explosives
• metal