Characteristic Particle
Definition
ASTM E1588 category: a single particle in which Pb, Sb, and Ba are simultaneously detected by EDS, with morphology consistent with melt-and-quench formation. Finding one or more on a sample supports a positive GSR conclusion.
- Standard
- ASTM E1588
- Elements required
- Pb, Sb, Ba simultaneously
- Detection
- EDS (energy-dispersive X-ray spectroscopy)
- Morphology
- Melt-and-quench consistent
Common questions
Does a single characteristic particle prove a person fired a weapon?+
One or more characteristic particles support a positive GSR conclusion, but examiners still weigh transfer, contamination, and environmental exposure possibilities before attributing the finding directly to firing versus secondary contact.
How does a characteristic particle differ from a consistent particle?+
A characteristic particle contains all three primer elements together in one particle, while a merely consistent particle shows only some of the elements or a partial composition, giving it lower specificity for primer discharge.
Related terms
- Antimony Sulphide
- Sb2S3, the primary fuel in conventional primer formulations, burning rapidly in the presence of oxygen released by barium nitrate during ignition.
- ASTM E1588
- ASTM International standard practice for gunshot residue analysis by scanning electron microscopy with energy-dispersive spectrometry. Defines particle classification (characteristic, consistent-with, indicative), morphology...
- Automated Particle Search (APS)
- A software-driven SEM mode that scans the entire stub surface using backscattered electron contrast, flags particles above an atomic-number threshold, and triggers...
- Barium Nitrate
- Ba(NO3)2, the oxidiser in conventional primer formulations, decomposing thermally to release molecular oxygen that sustains the combustion of antimony sulphide fuel.
- Consistent Particle
- ASTM E1588 category: a particle containing two of the three primer elements (Pb-Sb, Pb-Ba, or Sb-Ba), or all three elements without spherical...
- ENFSI EWG-GSR
- The European Network of Forensic Science Institutes Expert Working Group on Gunshot Residue. Produces best-practice manuals, proficiency test rounds, and guidance on...
- 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...
- Melt-and-Quench Mechanism
- The physical process by which GSR particles form: primer components are vaporised at firing temperatures, condense into spherical droplets in the expanding...
- Secondary Transfer
- The movement of a glass fragment from a primary surface (which contacted the broken glass) to a secondary surface (which contacted the...