Academic journal article Forensic Science Communications

Trace Evidence Recovery Guidelines

Academic journal article Forensic Science Communications

Trace Evidence Recovery Guidelines

Article excerpt

1.0. Scope

This guide describes procedures and techniques for the documentation, detection, collection, and preservation of trace evidence from crime scenes, individuals, and items submitted to the laboratory for examination.

2.0. Significance and Use

Locard's Exchange Principle states that whenever two objects come into contact, a transfer of material will occur (1). Trace evidence that is transferred can be used to associate objects, individuals, or locations.

2.1. The integrity and significance of trace material as associative evidence relies on proper detection, collection, and preservation.

2.2. An understanding of the transfer and persistence of trace evidence will assist the examiner in interpreting the significance of the analytical results.

3.0. Documentation

3.1. When a case is initiated, a file specific for that case must be created to contain the case documentation for the length of time required by the prevailing laws and nonconflicting agency policy.

3.2. Documentation of questioned and known trace evidence collection, whether done in a laboratory or at a scene, must include permanent notes about

a. date (and time, when appropriate) of the collection,

b. name of person or persons collecting the evidence,

c. a descriptive listing of item or items collected,

d. a unique identifier for each item collected such as an item number and case number, and

e. location of each item (documented by notes, sketches, measurements, photographs, or a combination of these).

3.3. The chain of custody for each item must be initiated upon collection and maintained until final disposition.

3.4. Recommended procedures for documenting and labeling physical evidence are outlined in ASTM Standard E 1459-92, Standard Guide for Physical Evidence Labeling and Related Documentation (9.2), and Standard E 1492-92, Standard Practice for Receiving, Documenting, Storing, and Retrieving Evidence in a Forensic Science Laboratory (3).

3.5. The principles of record initiation, maintenance, storage, and security are fundamentally the same for evidence collections within the laboratory and collections that may begin at a site remote from the laboratory.

4.0. Contamination and Loss

4.1. When collecting or examining items, care must be taken to prevent contamination and loss of trace materials.

4.2. If a case involves disciplines other than trace evidence, the involved examiners should confer before any work is undertaken. Unless circumstances dictate otherwise, the trace evidence should be collected and preserved prior to other examinations.

4.3. General principles and practices to avoid evidence contamination and loss, applicable to both laboratory and nonlaboratory settings, include the following:

4.3.1. Contact between items and personnel before the appropriate trace evidence has been secured should be restricted.

4.3.2. Appropriate protective apparel, such as laboratory coats and disposable gloves, must be worn to prevent contamination from the clothing of the examiner. The apparel must be changed as necessary to avoid contamination or transfer between evidentiary items, locations, and personnel.

4.3.3. Items being collected for trace evidence examination must be handled as little as possible to minimize loss of the trace evidence and to limit exposure of the items to contaminants.

4.3.4. Collect, package, and seal items individually in appropriate packaging. Keep items in a secure, sealed package until the item is processed in a controlled environment.

4.3.5. Equipment and work surfaces used during collection and examination must be cleaned in an appropriate manner before processing begins and as often as necessary during processing to prevent contamination.

4.3.6. Adhesive lift materials (used for collection, storage, or both) must be maintained in a manner to avoid contamination. …

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