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Development Color:
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Method to Record:
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Hazard:
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Protective Clothing:
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Fume Hood Use:
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Formula
Procedure of Application
Development Complete When
Source of Error
Incompatibilities
Precautions
Storage Container
Safety
Recommendations
Sequential Reagents
Formula
Formula "A" ( 1.0 % solution ): 1 g of Silver Nitrate 100 ml of distilled water Formula "B" (3.0 % solution): 30 g of Silver Nitrate 1000 ml of distilled water Formula "C" (Alcohol-based solution): 30 g of Silver Nitrate 100 ml of distilled water 1000 ml of Ethanol Procedure of Application
1. a) Tray immersion of item for 5 seconds. b) Reagent solution brushed onto item until coated. 2. Air dry for 20 minutes. 3. Sunlight or U.V. light exposure at 366 nm for ten to sixty minutes. Continuously monitor for development. Development Complete When
Discontinue the processing before any dark-brown background staining begins to cause the developed detail to loose contrast. Source of Error
Wet surfaces may have had their chloride components dissolved away. Silver Nitrate is a non-specific chloride developer. Incompatibilities
Items which have been wet may be leached of their chloride and salt impressions. Surfaces that have high chloride or salt compounds coating their surfaces or imbedded in them will produce unacceptable background staining. Precautions
High background staining may occur rapidly once the evidence is subjected to sunlight. Storage Container
Dark stoppered glass bottles. Safety
Use U.V. blocking eyewear when developing detail under U.V. light. Do not allow the reagent to contact your skin. Recommendations
Be sure to have the photographic set-up standing by once you begin the development process, else over-development may occur before you have a chance to photography the developed detail. Sequential Reagents
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Chemical Name
Silver Nitrate Surface Used On Porous Surfaces (Wood) that have not been wet Sensitive To Chloride & Salt Components Abridged Reagent Sequence
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Ridge Detail Visualized by:
Visible chemical/stain reaction Reagent Applicabilities: Porous Surfaces Ultra-Violet Light induced Other Chemical Name(s): None Working Solution Shelf-life: Twelve (12) Months |
Process Summary:
This process works by having sunlight develop the impression detail treated with the working solution. Background staining is a problem, thus the technique is not in wide use. The technique has its successes when used on wood surfaces that have not been treated with wax or varnish finishes.
This process works by having sunlight develop the impression detail treated with the working solution. Background staining is a problem, thus the technique is not in wide use. The technique has its successes when used on wood surfaces that have not been treated with wax or varnish finishes.
Accepted Deviations:
The concentration of the reagent may be increased up to 5%. Ultraviolet light can be used instead of sunlight to develop the detail. The working solution may be applied by spraying, dipping or brushing.
The concentration of the reagent may be increased up to 5%. Ultraviolet light can be used instead of sunlight to develop the detail. The working solution may be applied by spraying, dipping or brushing.
Supporting Reference Materials:
- Minutiae Magazine, Summer Special 1994, Issue No. 24, pg.7.
- "Chemical Formulas and Processing Guide for Developing Latent Prints", U.S. Dept. of Justice, pg. 47-48, 1994.
- Cowger, J.R. (1983), "Friction Ridge Skin", Elsevier, Page 99.
- Olsen, R.D. (1978), "Scott's Fingerprint Mechanics", Charles C. Thomas, Pg. 291.
- Keedwell, E., et. al. (1988), "Chemical Methods for Enhancement of Footwear Marks", Metropolitan Police Forensic Science Lab., Report No. 73, page 19.
- Cassidy, M.J., Footwear Identification, Lightning Powder Co., Salem, Oregon, pg.59, 1995.