Written by Tim Deakin

29th April 2025

• Cyber Security
• ISO 27001

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In any legal proceeding, evidence is key – and digital data lies at the heart of the evidence in many cases today. In order to preserve this crucial information, a chain of custody must be established to ensure that evidence remains intact, unchanged and preserved for scrutiny and analysis.

What is a chain of custody?

Generally speaking, a chain of custody refers to a documented trail to report on every step of the process from a piece of digital evidence being discovered through to being presented in court.

In cyber investigations, a chain of custody requires a detailed log of who has accessed the evidence, when, and if any changes were made (and if so, what these changes were). This process is crucial in proving that evidence has not been tampered with or compromised. Without keeping this documentation, evidence can be deemed unreliable and therefore inadmissible.

Why is it important?

In ensuring the integrity of digital evidence and admissibility, a chain of custody is essential. Without a reliable chain of custody, digital evidence’s authenticity can be brought into question which can lead to it being discounted by the court.

Just as a crime scene has procedures and protocols in place to ensure that it is preserved and recorded accurately, so digital data must follow a similar course of action. 

Moreso than physical evidence, digital evidence can be easily altered, so a clear and documented chain of its handling is essential. Meticulously documenting how, when and by whom digital evidence has been handled, investigators can demonstrate clearly whether the evidence has remained unaltered between collection and presentation.

What’s more, having a clear record of how data has been handled can help to highlight any gaps or vulnerabilities in your business’ data storage proceedings, helping you make positive changes for the future.

Documentation processes

A chain of custody can ensure the credibility of an investigation, avoiding poor documentation, incomplete logs and mishandled media. Creating a chain of custody requires several key steps, including:

• Evidence collection: documenting the conditions and locations where the evidence was found, including photographs, detailed notes and any additional contextual information.
• Evidence labelling: assigning unique identifiers to each piece of evidence, used consistently across all documentation.
• Evidence transfer: recording the date, time and personnel involved in every transfer of evidence. This involves detailed logs to cover any and all gaps in the chain of custody.
• Evidence storage: access logs of secure storage, which should be monitored. Again, it’s important to document who has accessed the data and when.  

Documentation tools often used by professionals include:

• Forensic imaging software: Digital forensics services like forensic imaging software can create exact copies of digital evidence, preserving a record of it at that specific place and time.
• Secure storage solutions: Ensuring evidence is kept safe from unauthorised access by utilising smart locks, video recording, and passkeys.
• Detailed logging systems: Comprehensive records of all actions taken, stored securely in a cloud-based platform with monitored access.

Best practice insights

Developing a protocol

Outlining the procedures for collecting, handling and storing digital evidence must include key steps for documentation and secure storage. Having a protocol in place will standardise investigations, ensuring all personnel are following the same procedure.

Training

A chain is only as strong as its weakest link, so ensuring all personnel involved in the investigation understand the chain of custody and its associated protocols is essential. Regular training sessions can reinforce best practices and keep team members informed.

Retaining file integrity

Key tools can be used to retain the integrity of evidence files, including write blockers (preventing modification to evidence during examination) and has validation (verifying hash values of digital evidence, making it easier to detect any alterations).

Forensic case management software

Forensic case management software can streamline documentation processes and provide secure storage for evidence logs, using features like automated logging, secure access controls, and evidence tracking.

If you’re looking for support with digital forensics services, contact SRM today.