Guidelines for Forensic Document Examination, Part 6, by SWGDOC (Forensic Science Communications, April 2000)
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April 2000 - Volume 2 - Number 2 |
Guidelines for Forensic Document Examination
Part 6
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Scientific Working Group for Forensic Document Examination (SWGDOC) |
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Revised January 2000 |
Guideline for the Safe Handling of Contaminated Document Evidence and the Preservation of Associated Trace Evidence
1. Purpose
To describe safe evidence-handling methods to preserve document evidence and other types of forensic material.
2. Introduction
2.1. This Guideline is intended for use when the preservation of document evidence must be considered when other forensic evidence coexists.
2.2. Terms defined in the glossary are in italics when they first appear in the Guideline.
3. Types of Evidence and/or Contaminants
3.1. Documents
3.2. Latent Prints
3.3. Biological Evidence
3.4. Trace Evidence
4. Requirements
4.1. That the forensic document examiner will have the following available:
4.1.1. Gloves (i.e., cotton, neoprene, latex).
4.1.2. Disposable dust mask or other type
of mask, if authorized.4.1.3. Indirect vented safety goggles.
4.1.4. Protective clothing (laboratory coats,
disposable sleeves, and booties).4.1.5. Fume hood.
4.1.6. Forceps, tweezers.
4.1.7. Paper storage bags, sealable transparent
document protectors, transparent archival quality
document protectors, biohazard labels.
5. Procedures
5.1. Items should be logged and identified using an appropriate writing medium, evidence labels, or other markings in accordance with established laboratory protocols.
5.2. Determine whether or not the items will be processed for latent prints (Section 6), contain trace evidence (Section 7), or contain biological contaminants (Section 8).
6. Procedures for Handling and Preserving
Latent Print Evidence
6.1. Whenever possible, original document evidence should be placed in clear protectors and examined through the protectors.
6.2. Cloth gloves should be worn when handling this type of evidence.
6.3. Any necessary identifying marks on the documents should be made in accordance with established laboratory policy.
6.4. A record copy should be made of the items (e.g., photograph, photocopy).
6.5. If indented impression examinations are required,they should be done prior to latent print processing.
6.6. If infrared studies are required, they should be done prior to latent print examinations or other processing, and photographs or photographic prints should be prepared to record significant results.
6.7. If solvents are to be used to visualize obliterations, only nonpolar organic solvents should be used prior to latent print processing.
6.8. Documents that have been processed for latent prints should be handled only with cloth gloves and placed in suitable protectors.
7. Procedures for Handling and Preserving
Items Containing Trace Evidence
Trace evidence should be removed by the appropriate forensic expert or forensic document examiner when the removal does not involve chemical or abrasive techniques. If chemical or abrasive techniques are necessary, this evidence should be removed only after making a record copy of the document and conducting indented writing, infrared, or other studies, when appropriate.
8. Procedures for Handling and Preserving Items Containing Biological Contaminants Evidence
8.1. Items contaminated with biological evidence should be handled with extreme caution. Masks, safety goggles, neoprene gloves, and protective clothing should be worn while handling contaminated documents. If possible, the items should be examined in a biological safety cabinet or fume hood.
8.2. Items contaminated with this type of material should be dried in a biological safety cabinet or fume hood.
8.3. If items cannot be examined immediately after drying and DNA analysis is requested, they should be placed in paper containers and stored in a freezer.
8.4. Biological evidence must never be stored in plastic containers.
8.5. Biological evidence must be protected from heat, humidity, ultraviolet light, and sunlight.
8.6. If it is necessary to remove the contamination in order to recover the handwriting or other questioned document evidence, the items should first be photographed.
8.7. If needed for later analysis, samples of the contaminant should be taken, preferably by an expert in that field.
8.8. Appropriate washing or other cleaning procedures may be applied after which the items should again be dried and placed in paper containers for storage.
8.9. After the examination is completed, all equipment and work surfaces should be cleaned and disinfected. A wipedown with household disinfectant, 70 percent isopropyl alcohol (rubbing alcohol), or 10 percent bleach will be adequate in most cases.
9. Examination Techniques for
Biologically Contaminated Document Evidence
(listed in ascending order of destructiveness, also refer to narrative)
9.1. Visual Examination. Nondestructive optical techniques should be tried first. These include use of transmitted light, ultraviolet light, infrared light, oblique light, and alternate light sources.
9.2. Humidity. It may be possible to soften and flatten soaked and dried documents using humidity.
9.3. Washing Solutions. Solutions may be used to remove biological fluids.
9.4. Abrasion. Scraping or abrasion may be used alone or with other techniques.
10. Examiner Safety
10.1. Forensic document examiners who examine biologically contaminated material should always wear appropriate protective clothing.
10.2. Forensic document examiners who examine biologically contaminated material should consider obtaining immunizations which include tetanus and hepatitis B.
11. Glossary
Biological Evidence: Any type of biological fluid including blood, urine, semen, feces, tissue, decomposition fluid, saliva, tears, mucus, perspiration, vomitus, and pus.
Document(s): In its fullest meaning, any material that contains marks, symbols, or signs either visible, partially visible, or invisible that may ultimately convey a meaning or message to someone. Pencil or ink writing, typewriting, or printing on paper are the more usual forms of documents.
Latent Prints: The most common type of biological contamination the document examiner will encounter. They are composed of skin secretions and pose no safety hazard.
Trace Evidence: Any type of nonbiological evidence that may adhere to the document surface such as hair, fibers, soil, glue, or paint.
Comments
Comments and questions concerning the Guideline for the Safe Handling of Contaminated Document Evidence and the Preservation of Associated Trace Evidence may be forwarded to Susan Morton at magnolia@worldspy.net.
Readers may also respond via a document comments form.
Discussion of the Guideline for the Safe Handling of Contaminated Document Evidence and the Preservation of Associated Trace Evidence
Introduction
Forensic document examiners are occasionally required to examine documents that are contaminated with biological or other material. Consideration must be given to the safety of the examiner and to the preservation of the evidentiary value of the contaminants. If possible, the forensic document examiner should confer with experts who might be performing tests of those contaminants after the document examination is completed. The following general guidelines should be followed in order to recover questioned document evidence and to preserve biological matter or other evidence for examination by other experts.
Latent Print Evidence
Latent prints are the most common type of biological contamination the forensic document examiner will encounter. Latent prints are composed of skin secretions and pose no safety hazard. The consideration in this instance is to preserve the evidence. Latent prints cannot be rubbed off paper, but they can be obliterated with superimposed impressions. Documents to be processed for latent prints should be placed in clear protectors and examined through the protectors as much as possible. Storage in plastic covers will not damage latent print evidence. The documents should be handled with cotton gloves. Neoprene gloves can leave marks which develop in certain types of latent print processing. Thin latex or vinyl gloves will mold to the fingertips and eventually act as a second epidermis capable of depositing the wearer’s finger impressions.
Any necessary identifying marks on the documents should be made in pencil. Pencil is impervious to the solvents used for latent print processing and will not be accidentally washed away during treatment. However, in the event that a latent print does develop in the marked area, the mark can be documented and then erased without disturbing the print.
In general, immersion in nonpolar organic solvents will not damage latent print evidence. These are the types of solvents used to carry the print-developing chemicals. The solvents include acetone, n-hexane, petroleum ether, and freon. Exposure to water or other aqueous solvents will diffuse prints so that they cannot be recovered. The forensic document examiner should be aware of this if using a visualizing solvent on an obliteration.
Should the forensic document examiner receive documents that have already been processed for latent prints, he or she should follow the procedures for handling chemically contaminated evidence. Unreacted chemicals in the paper can stain fingers, cause an allergic reaction, and develop newly deposited prints. Processed paper should be handled only with gloves and sealed in clear protectors as soon as possible.
Biological Contaminants
Biological contaminants include blood, urine, semen, feces, tissue, decomposition fluid, saliva, tears, mucus, perspiration, vomitus, and pus. All of these substances are capable of communicating human pathogens and should be handled with utmost caution. Masks, safety goggles, neoprene gloves, and protective clothing should be worn while handling documents contaminated with any of these contaminants. If possible, the evidence should be examined in a fume hood.
Items contaminated with this biological material should be dried in a fume hood. Drying retards decomposition, reduces likelihood of spreading contamination, and can render the items less offensive to examine. If objects cannot be examined immediately after drying, they should be placed in paper bags and stored in a freezer. Biological evidence must never be stored in plastic containers. In general, the enemies of biological evidence are heat, humidity, ultraviolet light, and sunlight.
Should it become necessary to remove the contamination in order to recover the handwriting or other questioned document evidence, the items should first be photographed. If needed for later analysis, samples of the contaminant should be taken, preferably by an expert in that field. Appropriate washing or other cleaning procedures may then be applied. The items should again be dried and placed in paper containers for storage.
After the examination is completed, all equipment and work surfaces should be cleaned and disinfected. A wipedown with household disinfectant, 10 percent bleach, or 70 percent isopropyl alcohol (rubbing alcohol) will be adequate in most cases.
Techniques for the Examination of
Biologically Contaminated Evidence
To some extent, the techniques selected will be determined by the type of examination to be done and the nature of the contaminants. Mere recovery of information may require less manipulation than performing a handwriting comparison. The following techniques are listed in ascending order of destructiveness.
Optical Examination
Nondestructive optical techniques should be tried first. These include use of transmitted light, ultraviolet light, infrared light, oblique light, and alternate light sources.
Humidity
It may be possible to soften and flatten soaked and dried documents using humidity. Humidity has the advantage of being unlikely to cause further damage to the evidence. However, it may increase the potential for exposure to pathogens. The document may be treated in a stream of steam or placed in a humidity chamber. A vaporizer or teakettle will provide a funneled stream source. This process should only be performed in a fume hood and with appropriate protective gear including neoprene gloves, mask, and protective garments.
Washing Solutions
Biological fluids are generally soluble in water. Soaking with gentle agitation in tepid water will often remove obliterating deposits. Warm or hot water should not be used because heat will fix protein and render it harder to remove. Alcohol or other solvents may also have this effect.
If the documents are hardened, a small amount of glycerin may be added to the wash water as a softening agent. The concentration of glycerin is not critical. A ratio of approximately five parts water to one part glycerin works well. Even after drying, the glycerin will leave the documents somewhat pliable.
Oils or lipids may be removed by adding a few drops of detergent to the wash water. Dishwashing liquid or shampoo may be used.
A weak solution of bleach may also be considered. One hundred (100) mL of household bleach (3 percent hypochlorite) in a liter of water is a good working solution. Bleach is an excellent disinfectant and will render the evidence safer to work with. However, it is a very powerful chemical and can damage the information to be recovered. Careful consideration should be given to its use.
Washing is a destructive technique and should be used only as a last resort. The material to be recovered may be removed along with the obliterating matter. Washing should be used only after all nondestructive methods have failed.
Abrasion
Scraping or abrasion may be used alone or with other techniques.
Immunizations
Forensic document examiners who examine biologically contaminated material should consider obtaining immunizations which include tetanus and hepatitis B. Hepatitis B is an incurable disease often lurking in biological material. Unlike the AIDS virus, which dies quickly outside the body, hepatitis B can remain viable in dried samples. Many employers will provide the immunizations. It must be emphasized that immunization is no substitute for proper handling of material. There are many diseases and strains of pathogens for which there are no cures and no vaccines. Prevention is the only safe course.
Comments
Comments and questions concerning the Discussion of the Guideline for the Safe Handling of Contaminated Document Evidence and the Preservation of Associated Trace Evidence may be forwarded to Susan Morton at magnolia@worldspy.net.
Readers may also respond via a document comments form.