Tertiary Transfer
Definition
Transfer of GSR from a secondary surface (a person who received particles via handshaking) to a third surface. Documented at low levels by Pun and Gallusser (2008) and generally produces very low particle counts.
- Mechanism
- GSR moving from a secondary to a third surface
- Typical yield
- Very low particle counts
- Key reference
- Pun and Gallusser, 2008
- Field
- GSR sampling and secondary transfer studies
Common questions
Why does tertiary transfer matter in court?+
Because it can explain a small number of GSR particles on someone who never fired or handled a firearm, defence experts raise tertiary transfer to argue that low particle counts do not prove direct contact with a discharged weapon.
How does an examiner distinguish tertiary transfer from direct discharge?+
Particle count and morphology help, since direct discharge typically deposits far more particles with characteristic spherical morphology, while tertiary transfer yields only a handful, but the distinction is probabilistic rather than absolute.
Related terms
- 5% HNO3 Swab
- A cotton or polyester swab pre-wetted with 5% nitric acid, used to collect dissolved GSR for atomic absorption spectrometry or ICP-MS. Recovers...
- Carbon-Tape Stub (Tri-Mark)
- A standard SEM-format aluminium or plastic pin stub bearing conductive double-sided carbon tape, used to collect GSR from hands and surfaces for...
- Environmental Control Stub
- A blank carbon-tape stub collected from the collection environment (table surface, custody cell, vehicle seat) to establish background particle levels in the...
- NABIS (National Ballistics Intelligence Service)
- The UK agency responsible for managing ballistic evidence including GSR analysis, operated by the National Police Chiefs' Council. Issues guidance on GSR...
- Persistence Half-Life (GSR on Hands)
- The time after which approximately half of the initial particle count has been lost from the hand surface. Published studies (Cardinetti 2004,...
- Secondary Transfer
- The movement of a glass fragment from a primary surface (which contacted the broken glass) to a secondary surface (which contacted the...