- 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
The Modified Griess Test is carried out as follows:
- Confirm nitrite sensitivity of test paper.
Using a nitrite test swab saturated with 15 percent acetic acid solution, dab the corners of the test paper. Each corner should turn orange, confirming the sensitivity of the paper to nitrite compounds. A negative control should also be tested for each sheet of photographic paper to ensure that it is not contaminated. - Mark reference points of evidence on test paper.
Place the evidence face down on the emulsion-coated side of the test paper. Using a pencil, index any seams, button holes, buttons, rips, pockets, suspected bullet holes, tears, cuts, etc., for reference. Do not use ink because it may transfer back onto the evidence item. - Create layers of reaction items.
Soak an unused piece of cheesecloth in the acetic acid solution. Wring excess solution from the cheesecloth and spread it on top of the evidence (already placed on the photographic paper), completing the three-layer sandwich. - Heat reaction layers.
Press the layers with a hot uncontaminated iron. Acetic acid steam is forced through the layers, causing the color-producing reaction. - Examine and interpret the results.
Discard the cheesecloth and separate the evidence item from the test paper. Any orange indications on the paper are the result of a chromophoric reaction chemically specific for the presence of nitrite residues.
Note: It is possible that a spurious source of nitrite residues (not firearms-related) could be present. These are typically visualized as an orange haze; it is unlikely that such residues would alter the interpretation of the point reactions around a suspected bullet hole. Occasionally, background reactions can be observed on clothing items made from blue denim and from garments washed using certain detergents. Some disinfectants, as well as marijuana, can yield positive results. - Label and retain test paper.
Mark the previous pencil marks placed on the test paper in ink when the paper is dry. Label with additional data as called for by laboratory protocol.
Click here to watch a video on the Modified Griess Test procedure
