- 01: Introduction
- 02: History
- 03: Propellants, Firearms, and Ammunition Development
- 04: Modern Firearms Manufacture
- 05: Small Arms Ammunition
- 06: Evidence Handling Procedures
- 07: Equipment and Instrumentation
- 08: Examination of Firearms
- 09: Cartridge and Shotshell Examination
- 10: Characterization and Evaluation of Fired Projectiles
- 11: Bullet Comparison and Identification
- 12: Gunshot Residue and Distance Determination
- Introduction
- Objectives
- AFTE Knowledge and Ability Factors
- Powders and Residues
- Examination
- Distance Determination
- Significance of Results
- Contact Shot
- Nitrite Residues
- Vaporous Lead Residues
- Residues Consistent with the Passage of a Bullet
- Residues Consistent with the Discharge of a Firearm
- Interpretation Challenges
- Reproduction of Results
- Nitrite Residue Patterns
- Shot Patterning
- Chemical Testing
- Shot Pattern Reproduction
- Selected Bibliography
- 13: Toolmark Identification
- 14: Communicating Results
- Resources
Test Procedure
Home > Gunshot Residue and Distance Determination > Examination > Chemical Testing > Test Procedure
Test area with fume hood
This test procedure involves applying chemical reagents using aerosol sprays. This can be readily accomplished using cans of compressed gas. All spraying should be performed in a chemical fume hood.
The Sodium Rhodizonate Test is carried out as follows:
- Confirm performance of all preliminary examinations and tests.
The Modified Griess Test and the Dithiooxamide Test must be performed before this test. - Place a test mark on the item to be tested.
Using a known piece of lead, place the mark well away from any areas to be tested.
(Note: Apply the following steps to the test mark first to ensure the reagents are reacting properly and then apply to the questioned area.) - Position the area to be tested.
Place the test mark or suspected bullet hole face up on a clean uncontaminated surface. - Perform color test.
- Spray the test area with the saturated solution of sodium rhodizonate.
- Spray the same area with the buffer solution.
This solution eliminates the yellow background color caused by the sodium rhodizonate, establishes a pH of 2.8, and displays a pink color in the presence of lead and some other heavy metals. - Spray the same area with the hydrochloric acid solution.
The pink color fades leaving a blue-violet color, indicating the presence of lead.
This result can fade quickly; observations should be photographed and documented promptly.
Click here to watch a video on the Sodium Rhodizonate procedure
