Organic GSR (OGSR)
Definition
Propellant-derived residues including nitroglycerin, 2-NDPA, 4-NDPA, ethyl centralite and nitrocellulose fragments. Analysed by HPLC or GC-MS, independent of the inorganic SEM-EDS workflow.
- Key compounds
- Nitroglycerin, 2-NDPA, 4-NDPA, ethyl centralite, nitrocellulose
- Origin
- Propellant, not primer
- Analysed by
- HPLC or GC-MS
- Relation to inorganic GSR
- Separate, independent workflow from SEM-EDS
Common questions
Why analyse organic GSR separately from the standard SEM-EDS gunshot residue test?+
SEM-EDS detects inorganic primer residue particles such as lead, barium and antimony, which come from the cartridge primer, while organic GSR compounds come from the propellant charge and require a different chemistry entirely. Some modern ammunition uses heavy-metal-free or lead-free primers, so organic GSR testing can detect a discharge that SEM-EDS would miss.
What does finding organic GSR compounds on a suspect actually indicate?+
It indicates exposure to propellant combustion products consistent with a firearm having been discharged nearby or handled shortly after discharge, but like inorganic GSR it cannot by itself identify who pulled the trigger, since transfer and contamination are possible.
Related terms
- ASTM E1588-20
- ASTM International standard guide for gunshot residue analysis by SEM-EDS. Defines characteristic, consistent, and commonly-associated particle categories and sampling, analysis, and reporting...
- Automated SEM-EDS
- A robotic scanning electron microscopy workflow using backscattered electron imaging for morphometric screening and automated EDS acquisition for elemental classification. Reduces analysis...
- Characteristic GSR Particle (ASTM E1588-20)
- A particle containing lead, barium and antimony together by SEM-EDS, with spherical morphology and size in the 0.5-10 micrometre range. The highest-specificity...
- DDNP (Diazodinitrophenol)
- A lead-free primary explosive used in some lead-free primer formulations. Produces strontium-antimony or tin-containing GSR particles depending on the oxidiser used.
- Lead Styphnate
- Lead trinitroresorcinate (Pb(C6H(NO2)3O2)), the primary explosive in conventional primer compounds. Co-oxidised with barium nitrate and antimony sulfide to produce the Pb-Ba-Sb triad...
- SINTOX
- A lead-free, heavy-metal-free primer formulation developed by DAG (Deutsche Ammunitions- und Geschossfabrik) and Geco in Germany in the 1990s-2000s, replacing lead styphnate...
- Ternary Diagram (Pb-Ba-Sb)
- A triangular compositional plot with Pb, Ba and Sb at the three vertices. Particles from conventional primer discharge cluster in the centre;...