What Is Chain of Custody in Digital Forensics? Steps & Best Practices

Chain of custody in digital forensics is the documented record of how digital evidence is identified, collected, acquired, handled, transferred, stored, and examined during an investigation.

Unlike physical evidence, digital data can be copied or modified without obvious physical signs. For this reason, forensic investigations may use procedures such as forensic acquisition, write protection, hash verification, controlled storage, and detailed documentation to help preserve and demonstrate evidence integrity.

What Is Chain of Custody in Digital Forensics?

A chain-of-custody record is a detailed record that shows where digital evidence has been, who handled it, and what was done with it from the time it was collected until it was examined and stored.

It can document:

• Evidence ID
• Device or evidence description
• Serial number or other identifier
• Collection date, time, and location
• Collector
• Initial condition
• Acquisition method
• Relevant hash values
• Storage location
• Transfers and recipients
• Reason for each transfer
• Examination details

NIST describes chain of custody as tracking evidence through collection, safeguarding, and analysis while recording who handled it, relevant dates and times, and the purpose of transfers.

Chain of Custody vs. Evidence Integrity

These concepts are related but different.

Chain of custody documents:

Who handled the evidence, when, where, and why?

Evidence integrity concerns:

Whether the digital data can be shown to have remained unchanged or whether changes are known and documented.

Hash verification, forensic acquisition, and write protection can support evidence integrity. They do not replace the chain-of-custody record.

Why Is Chain of Custody Important?

Digital evidence can pass between investigators, forensic examiners, laboratories, and storage locations.

A documented chain of custody helps establish:

• Accountability: who handled the evidence
• Traceability: where the evidence went
• Documentation: what happened during handling
• Integrity support: how preservation and verification were performed
• Reproducibility: how the examination was conducted

The legal effect of a custody issue depends on the evidence, circumstances, applicable rules, and jurisdiction. A documentation gap should not automatically be described as making evidence inadmissible.

What Should a Digital Chain-of-Custody Form Include?

A typical record may include:

This is a sample only. Actual documentation requirements depend on the investigation, organization, and applicable procedures.

What Are the Steps in a Digital Chain of Custody?

The exact workflow varies by evidence type, but a typical process includes the following steps.

1. Identify the Evidence

Document what was collected and assign a unique evidence ID.

For a device, record relevant information such as:

• Manufacturer and model
• Serial number or IMEI
• Physical condition
• Location
• Power state
• Connected devices or accessories

Photographs and contemporaneous notes can also document the initial condition.

2. Consider the Order of Volatility

Some digital information can disappear or change quickly.

Potentially volatile evidence can include:

• RAM
• Active network connections
• Running processes
• Temporary system information

Investigators may consider volatility when determining collection priorities. There is no single sequence that applies to every investigation; the approach depends on the system and circumstances.

3. Collect and Document the Evidence

Record:

• Who collected it
• Where and when it was collected
• How it was collected
• Device condition
• Power state
• Actions performed during collection

For live systems, the investigator should also document relevant actions taken to capture volatile information.

4. Preserve the Original Evidence

Protect the original evidence from unnecessary modification.

Depending on the evidence, this may involve:

• Controlled access
• Secure storage
• Write protection
• Forensic acquisition
• Evidence tracking
• Verification records

5. Create a Forensic Image or Appropriate Acquisition

For storage media, investigators may create a forensic image or another appropriate forensic acquisition instead of conducting routine analysis directly on the original media.

The acquisition record should identify the source evidence, acquisition method, relevant tools, examiner, date/time, and verification information.

NIST SP 800-86 provides established guidance on forensic techniques but states that it is not an all-inclusive forensic investigation procedure or legal advice.

6. Use Write-Blocking Where Applicable

A write-blocker prevents data from being written to subject media while allowing investigators to examine it. This can reduce the risk of unintended modification during certain acquisition or examination procedures.

Write-blocking is not a universal requirement for every digital evidence source. Its use depends on the evidence and acquisition method.

7. Calculate and Verify Hashes

A cryptographic hash produces a value based on digital data.

An examiner can calculate a hash for an acquired image and record the result. The hash can later be recalculated and compared with the original value.

A matching hash indicates that the data used for the comparison produces the same digest.

A different hash requires investigation. It does not automatically prove intentional tampering.

8. Document Every Transfer

When evidence changes possession or control, document:

• Who released it
• Who received it
• Date and time
• Evidence ID
• Purpose of transfer
• Storage location
• Condition, where relevant

This maintains the chronological custody record.

9. Examine and Report the Evidence

The examiner analyzes the appropriate acquisition or evidence and documents the methods, tools, findings, and supporting artifacts.

Depending on the investigation, this may involve:

• Deleted files
• Metadata
• Email
• Browser artifacts
• Application data
• System logs
• Documents
• Images
• Mobile data
• Network information

ISO/IEC 27042:2015 provides guidance on the analysis and interpretation of digital evidence, including documentation, reproducibility, and repeatability.

How Does Hashing Help Protect Digital Evidence Integrity?

Hashing is useful because changes to digital data can result in a different hash value.

For example:

Forensic acquisition → SHA-256 hash → recorded value → later verification

If the expected hash is reproduced, the compared data is consistent with the previously hashed data.

However, a hash does not prove:

• Who originally collected the device
• Whether the correct device was collected
• Who handled it before hashing
• Whether the acquisition procedure was appropriate
• Whether the chain-of-custody documentation is complete

Hash verification is therefore a technical integrity control, not a replacement for chain-of-custody documentation.

Types of Digital Evidence

Chain-of-custody procedures can apply to different types of digital evidence.

Computer and Hard Drive Evidence

Computer and hard drive evidence may include documents, system logs, registry artifacts, deleted files, and unallocated space. If a drive is damaged or failing, forensic hard drive recovery is performed first to preserve the original media before analysis.

Relevant controls: device identification, forensic acquisition, write protection where applicable, hashing, and secure storage.

Mobile Device Evidence

Mobile devices can contain call logs, messages, app data, location artifacts, and deleted records. Because messaging data can be important in disputes, forensic text message recovery requires proper evidence handling: preserve first, acquire second, and document every step.

The examiner should document the device condition and acquisition method.

Cloud Evidence

May include account records, cloud files, email, audit logs, access records, and metadata.

Documentation should identify the source, acquisition/export method, timestamps, and preservation process.

Email and Digital Documents

In email and document eDiscovery, relevant evidence may include headers, timestamps, attachments, metadata, document properties, and original files. Proper collection and preservation can help maintain the context and evidentiary value of these records.

Network and Log Evidence

May include authentication logs, firewall records, server logs, endpoint logs, and security alerts.

The source, collection method, timestamps, and preservation process should be documented.

Common Chain-of-Custody Mistakes

Common problems include:

• Missing evidence IDs
• Missing collection or transfer times
• Unidentified handlers
• Incomplete transfer records
• Poor storage controls
• Inconsistent device identifiers
• Incomplete acquisition documentation
• Missing or incorrect hash records
• Uncontrolled interaction with original media
• Unexplained documentation gaps

These issues can make the evidence history harder to reconstruct and may raise questions about evidence handling or integrity.

What Happens If There Is a Gap in the Chain of Custody?

A gap occurs when the evidence-handling record is incomplete or contains an unexplained inconsistency.

Examples include:

• Missing transfer records
• Unidentified handlers
• Conflicting timestamps
• Unexplained storage periods
• Inconsistent evidence identifiers

The significance of a gap depends on the evidence and circumstances. Investigators should document the discrepancy and determine whether other records can establish what happened.

Possible supporting records include:

• Access logs
• Storage records
• Acquisition records
• Examiner notes
• Hash verification
• Transfer documentation

The legal consequences depend on the applicable rules and jurisdiction.

Real-World Digital Forensics Case Example

TechFusion has described a case involving a mobile phone that was reported as water-damaged and beyond recovery.

During the forensic examination, the team’s findings did not support that characterization. After restoring the device by our Mobile device forensics experts, TechFusion reported recovering hundreds of text messages, call logs, and timestamped activity.

The recovered information helped reconstruct a clearer timeline and identify inconsistencies in the original investigation.

The case illustrates why documenting the condition, handling, preservation, and examination of digital evidence matters throughout a forensic investigation.

Read the detailed Greg Hart digital evidence case for the full investigation.

Digital Chain-of-Custody Best Practices

1. Assign a unique evidence ID.
2. Document the original condition.
3. Record collection date, time, and location.
4. Identify the collector.
5. Record relevant device identifiers.
6. Consider volatile data before collection.
7. Protect original evidence from unnecessary modification.
8. Use appropriate write protection where applicable.
9. Create an appropriate forensic acquisition.
10. Record relevant hash values.
11. Secure evidence against unauthorized access.
12. Document every transfer.
13. Maintain examination records.
14. Preserve supporting documentation.
15. Report findings based on the documented evidence and methodology.

Standards and Guidance

NIST SP 800-86

NIST SP 800-86, Guide to Integrating Forensic Techniques into Incident Response, provides guidance on integrating forensic techniques into incident response. It covers sources including files, operating systems, network traffic, and applications. NIST states that it is not an all-inclusive forensic investigation procedure or legal advice.

ISO/IEC 27037:2012

ISO/IEC 27037:2012 provides guidelines for the identification, collection, acquisition, and preservation of potential digital evidence.

ISO/IEC 27042:2015

ISO/IEC 27042:2015 addresses the analysis and interpretation of digital evidence, including documentation, reproducibility, repeatability, and independent scrutiny.

These resources provide technical guidance but do not replace jurisdiction-specific legal requirements or an organization’s forensic procedures.

Need Help With Digital Evidence?

Proper evidence handling requires more than documentation. TechFusion provides digital forensic services to help identify, preserve, acquire, and analyze digital evidence using appropriate forensic procedures. If you need assistance with a digital investigation or evidence examination, contact TechFusion to discuss your case with a forensic professional.

Frequently Asked Questions

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