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CJIS-Security & Control

Chain of Custody and Evidentiary Integrity for Digital Evidence

21 September 2025By Bilal Ahmed
CJISChain of CustodyEvidentiary IntegrityDigital EvidenceArchivesCompliancePublic Safety

Introduction

Digital evidence — such as body-worn camera footage, dashcam recordings, surveillance media, and mobile device data — plays a pivotal role in modern investigations and prosecutions. To be admissible in court, this evidence must be handled with strict attention to chain of custody and evidentiary integrity. This blog explores best practices for ensuring digital evidence stored in archives meets compliance and legal standards, particularly under CJIS Security Policy.

What is Chain of Custody?

Chain of custody refers to the documented, unbroken record of who collected, handled, transferred, or accessed evidence throughout its lifecycle.

Key Elements:

  • Documentation: Every interaction must be logged (who, when, why, how).
  • Continuity: Evidence must be tracked from collection to final disposition.
  • Accountability: Each custodian is responsible for safeguarding integrity while in possession.

Ensuring Evidentiary Integrity

Evidentiary integrity means the digital evidence has not been altered, tampered with, or compromised.

Best Practices:

  1. Immutable Storage: Use WORM (Write Once, Read Many) or blockchain-backed immutability to prevent modification.
  2. Cryptographic Hashing: Generate and validate hash values (e.g., SHA-256) to prove files remain unchanged.
  3. Encryption: Secure evidence in transit and at rest with FIPS-validated encryption.
  4. Access Controls: Restrict evidence access to authorized personnel only.
  5. Audit Trails: Maintain immutable logs of every access, export, or transfer.

Mapping to CJIS Security Policy

  • Audit & Accountability: Requires tracking access to all CJI, including digital evidence.
  • Cryptographic Controls: Enforces encryption and integrity validation for evidence.
  • Access Control: Applies role-based access and least-privilege principles to evidence archives.

Challenges

  • High Data Volumes: Bodycam and surveillance video generate massive archives.
  • Inter-Agency Transfers: Evidence often needs to be shared across jurisdictions.
  • Human Error: Manual handling increases risk of breaks in chain of custody.

Best Practices

  1. Automate Logging: Use digital systems to automatically record chain of custody events.
  2. Standardize Workflows: Create uniform evidence handling procedures across agencies.
  3. Secure Transfers: Use CJIS-compliant, encrypted channels for evidence sharing.
  4. Periodic Validation: Re-hash stored evidence periodically to confirm integrity.
  5. Train Personnel: Educate staff on evidentiary handling, documentation, and legal defensibility.

Conclusion

Maintaining chain of custody and evidentiary integrity is critical for digital evidence to be admissible and defensible in court. By combining immutable storage, encryption, cryptographic hashing, and rigorous audit logging, agencies can protect sensitive digital records while ensuring compliance with CJIS and maintaining public trust.