Trace Materials Crime Scene Investigation Guide

Introduction

• The guide is a draft by the Organization of Scientific Area Committees for Forensic Science (OSAC).
• Aimed at helping forensic scientists and stakeholders.
• Intended for future development into a web application.

Trace Evidence Overview

• Trace evidence helps establish associations between people, places, and objects.
• Small, variable, and easily transferable, making it hard to recognize and potentially lost.

Purpose of the Guide

• Assist crime scene investigators in recognizing, collecting, and packaging trace evidence.
• Provides a reference table and detailed chapters on different evidence types.
• Focuses on trace evidence while maintaining the integrity of other evidence types.

Evidence Collection and Packaging

• Submit entire items when practical; collect known samples as close to the incident as possible.
• Package each item separately; use appropriate containers to prevent contamination and loss.

Sub-disciplines

• Airbags
• Explosives
• Fibers (including fabric damage and impressions, cordage)
• Fire Debris
• Footwear and Tire Impressions
• Geological Material
• Glass
• Gunshot Residue
• Hairs
• Lamp/Filaments
• Paint
• Physical Fit
• Tape
• Other Types of Trace Evidence

Types of Crime Scenes

• Arson
• Shooting
• Stabbing
• Manual Strangulation
• Asphyxiation
• Blunt Force Trauma
• Sexual Assault
• Dumped Body
• Wrapped or Bound Victim
• Burglary
• Suspicious Death
• Explosion
• Hit-and-Run

Collection and Packaging Techniques

• Use airtight containers for volatile substances.
• Use paper bags for clothing and avoid plastic bags for fibers and fabrics.
• Special considerations are needed for explosive materials, fire debris, and biological samples.

Specific Evidence Types

Airbags

• Residue particles are deposited on occupants during deployment.
• Collect airbag residue particles using GSR kits.

Explosives

• Determine chemical composition and device functionality.
• Handle with extreme caution; package in airtight containers.

Fibers and Fabrics

• Examine fibers for type, color, and material associations.
• Collect entire items or use tweezers/sticky notes for loose fibers.

Glass

• Submit entire items or collect fragments with leak-proof packaging.

Gunshot Residue

• Collect using adhesive lifters, focusing on hands and clothing.

Hairs

• Known samples should be collected for comparison.
• Store in paper folds or envelopes to prevent loss.

Lamp Filaments

• Determine if lamps were on or off during an impact.
• Submit entire lamp assemblies or individual bulbs.

Paint

• Collect known and questioned samples for a detailed comparison.

Physical Fit

• Pieces with irregular edges can be physically matched to ascertain common origins.

Tape

• Compare physical and chemical properties for source associations.

Other Trace Evidence

• Includes building materials, animal parts, botanicals, and more.
• Collection methods vary based on material type.

General Precautions

• Prevent contamination using new and/or clean packaging materials.
• Dry wet materials prior to packaging.
• Use disposable gloves and clean tools.

Laboratory Capabilities

• Forensic labs conduct analyses for identification, comparison, and material characterization.
• Specific techniques are used based on the type of evidence.

Applicable Scene Types

• Trace evidence is applicable to a wide range of crime scenes including arson, death investigations, and hit-and-run cases.