Comprehensive Notes on Terrestrial LiDAR Scanners in Criminal Justice Applications

Technical Contacts

Michael Russ, MS
Sheriff's Lead Crime Scene Specialist
Email: mruss@sbcsd.org

Rebecca Shute, MS
Email: rshute@rti.org

Lance Miller
Email: lmiller@rti.org

John Grassel, MS
Email: jgrassel@rti.org

Acknowledgments

This publication is a culmination of collaborative efforts from a diverse group of forensic practitioners and researchers who have extensive backgrounds in crime scene documentation, reconstruction, and analysis. These experts have provided invaluable input on methodologies and best practices related to forensic science, particularly in the areas of bloodstain pattern analysis and trajectory reconstruction. The working group includes representatives from various jurisdictions, committees, and specialized task forces, reflecting a wide range of experiences and perspectives in forensic investigation and legal compliance.

Public Domain Notice

Material in this publication is in the public domain and can be reproduced without permission from the Department of Justice (DOJ). However, unauthorized alterations or sales for profit require written authorization from the original publisher to protect the integrity of the information presented.

Suggested Citation

Forensic Technology Center of Excellence. (2022). Guidelines for the Use of Terrestrial LiDAR Scanners in Criminal Justice Applications. Research Triangle Park, NC: RTI International. This document serves as a crucial resource for law enforcement officials and forensic analysts in effectively applying cutting-edge technology in their investigations.

Table of Contents

2. Foreword

3. Scope

4. Terms and Definitions

   • 3D Imaging System

   • Calibration

   • Accuracy

   • Error

5. Technology Overview

   • Introduction to LiDAR technology and its applications in crime scene reconstruction.

6. Equipment Calibration

   • Calibration Frequency: Typically every 1-2 years to ensure optimal performance.

   • Self-Calibration: New devices claim self-calibration features, enhancing user convenience.

7. Equipment Validation

   • Periodic Calibration Verification: Standard (ISO 17123-9) must be adhered to, ensuring compliance with international quality benchmarks.

8. Personnel Capabilities, Training, Experience, and Qualifications

   • Definitions of functional roles: Operator, Technologist, Analyst, highlighting respective responsibilities.

   • Minimum Training Requirements for each role ensuring competency and efficiency in operation.

9. TLS Data Capture

   • Applications: Critical measurements, general analysis, and demonstrative use in court proceedings.

   • Key steps in preparing for a scan: security measures, settings optimization, and reflective surface preparation.

10. Data Processing

    • Registration: Aligning scans for cohesive analysis to build a unified perspective of the scene.

    • Outlier Removal: Managing extraneous data captured during scans, crucial for maintaining forensic clarity.

11. Data Management

    • Types of data and best practices for integrity and storage, crucial for preserving evidence.

12. Disclosure of Data

    • Legal requirements and recommendations for trial preparation, ensuring admissibility and transparency in legal contexts.

Key Concepts

LiDAR Technology: Acquires geometric data to capture detailed 3D representations of crime scenes. This technology is particularly useful for documentation, trajectory analysis, and visual evidence in court.

Calibration & Validation: Essential for maintaining high measurement precision. Adherence to manufacturer specifications and relevant standards is crucial to ensure reliability during investigative analysis.

Documentation Procedures: Effective documentation is vital for preserving the integrity of scans; should include comprehensive details such as weather conditions, operator notes, calibration dates, and any discrepancies noticed during the scanning process.

Data Integrity: The use of hash values ensures that data has not been altered over time, maintaining the legitimacy of the evidence collected. Documentation and storage protocols are also important for evidence admissibility in legal proceedings.

Training and Expertise: Operators must undergo rigorous training specific to TLS instruments and their functionalities. Regular proficiency testing and continuous professional development are recommended as part of quality assurance to maintain competency.

Legal Considerations: Proper legal protocols must be observed for TLS evidence to be admissible in court. This includes stringent requirements for evidence authentication and transparency in its handling to uphold legal standards.

Technology Overview

Three Types of TLS Devices:

2. Tripod-mounted laser scanners: These are known for their accuracy and precision, ideal for capturing critical details during crime scene documentation.

3. SLAM devices: These are typically used for scanning larger areas where some accuracy may be sacrificed for improved speed and efficiency, particularly in dynamic environments.

4. Handheld laser scanners: Best suited for small, detailed measurements and confined spaces where mobility is needed.

Functional Applications: TLS technology is utilized across various forensic contexts, enhancing the capability of analysts to visualize and recreate crime scenes or incidents accurately, facilitating effective communication of findings in legal settings.

TLS Data Capture Preparation

Security: Establish scene security thoroughly before scanning. Define perimeters to avoid any disturbances that could compromise the scene's integrity and to safeguard evidence.

Environmental Considerations: Weather conditions can significantly impact the quality of scans; hence, operators should be prepared to adjust settings accordingly to ensure optimal data acquisition.

Reference Measurements: These are essential to ensure measurement validation using NIST (National Institute of Standards and Technology) traceable artifacts, thus maintaining the accuracy and integrity of the data collected.

Data Processing Workflow

Data Import: The data processing initiation is specific to manufacturer software; therefore, a deep understanding of available filters and their functions is crucial for effective data management.

Registration: This process is key to creating a unified point cloud from multiple scans, ensuring cohesive analysis and accurate representation of the crime scene.

Outlier Management: Care must be taken to identify and handle data points resulting from transient individuals or extraneous objects that might confuse or compromise the clarity of the evidence collected.

Documentation: It is imperative to maintain comprehensive records of processing steps, registration accuracy, and data integrity checks to support validity in court and ensure transparency in forensic procedures.

Training: Ongoing education on the latest TLS technology advances is critical for users to effectively apply these techniques and relay findings accurately in legal contexts.