Test-Fire Envelope
Definition
The set of reference targets produced by firing the case weapon (or a ballistically equivalent substitute) loaded with the same ammunition at calibrated distances, processed with the same chemical tests as the case evidence. Defines the distance boundaries for the forensic chemist's range opinion.
- Purpose
- Set distance boundaries for a firing-range opinion
- Method
- Firing the case weapon at calibrated distances
- Held constant
- Ammunition and chemical test method
- Field
- Firing distance chemistry (Griess, sodium rhodizonate)
Common questions
Why must the same ammunition be used for the test fires?+
Propellant load, primer composition and bullet type all affect how far residue travels, so testing with different ammunition than the case round would produce a distance envelope that does not match the evidence being interpreted.
What if the exact case weapon is unavailable for testing?+
An examiner can substitute a make and model documented as ballistically equivalent, but this introduces additional uncertainty into the range opinion compared with testing the actual weapon recovered in the case.
Related terms
- Azo Dye
- A class of organic dyes containing one or more azo groups (R-N=N-R'). Formed in the Griess test by coupling of a diazonium...
- BSA 2023 (Bharatiya Sakshya Adhiniyam)
- India's evidence statute enacted in 2023, replacing the Indian Evidence Act 1872. Sections 39-46 govern expert testimony, including the admissibility and presentation...
- Contact Wound
- A firearm wound produced when the muzzle is pressed against or within a few centimetres of the target surface. Characterised by a...
- DeHaan Modification
- A refinement of the Griess test procedure for forensic propellant residue detection, using a combined sulphanilic acid + NEDA reagent on filter...
- Modified Griess Test
- A contact-transfer colour chemistry test for nitrite-containing propellant combustion residue. Sulphanilic acid undergoes diazotisation with nitrous acid (from NO2 on the target...
- NEDA (N-(1-Naphthyl)ethylenediamine Dihydrochloride)
- The azo coupling component in the modified Griess test. After diazotisation of sulphanilic acid with nitrous acid, NEDA couples with the diazonium...
- NIJ Range Estimation Guidelines
- NIJ Standard 0612.00 (US National Institute of Justice). The primary US guidance document for firing-distance determination methodology, covering test-fire protocols, pattern comparison...
- Sodium Rhodizonate
- A chelating agent producing a scarlet-to-red colour with lead ions at acid pH. Applied to entry-wound margins and garment entry holes to...
- Stippling (Tattooing)
- Discrete punctate abrasions or haemorrhages around an entry wound from individual unburned propellant granules embedding in the epidermis at intermediate range. Unlike...