Guide for Casting Footwear and Tire Impression Evidence

1. Scope

1.1 This Guide provides procedures that should be used for the casting of footwear and tire impression evidence.

1.2 The particular procedures and methods employed in a given case will depend on the evidence.

1.3 This Guide may not cover all aspects of unusual or uncommon conditions.

1.4 This Guide does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this Guide to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

1.5 This Guide is not intended as a substitute for training in the casting of footwear and tire impression evidence. Completion of a training program and experience in these skills is essential to understanding and applying the principles outlined in this Guide.

1.6 This Guide relates to the casting of footwear and tire impressions as part of the collection of impression evidence for examination in the laboratory.

2. Terminology

Denial stone: a gypsum product used to cast impressions

Fixative: any product that will stabilize the substrate prior to casting

Impression: the product of direct physical contact of an item resulting in the transfer and retention of characteristics of that item

Release agent: any product that prevents soil from adhering to the cast

Snow Print Wax: a spray wax used to coat the surface of snow impressions prior to casting

3. Significance and Use

3.1 The procedures outlined here are grounded in the generally accepted body of knowledge and experience in the casting of footwear and tire impression evidence. By following these procedures, impressions can be properly cast.

3.2 Footwear and tire impressions are cast for the purpose of collecting impression evidence.

4. Interferences

4.1 Footwear and tire impression evidence may have inherent limitations that can interfere with the procedures in this Guide. Limitations, when known, should be noted and recorded.

4.2 Limitations can be due to substrate features, environmental conditions, quality and quantity of original impressions, casting techniques and casting materials.

5. Equipment and Requirements

5.1 Casting materials (e.g., dental stone and sulfur)

5.2 Zip-lock bags and mixing containers

5.3 Water

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