Cloud Storage Forensics, Expert Testimony, and Evidentiary Reliability

Contributed by Kris Carlson, COO, Former ICAC Commander, Digital Forensics Investigator, and Testifying Expert

Series context. Part 2 of the Forensics and Futures 2026 series examines how cloud storage systems reshape digital evidence, expert testimony, and evidentiary risk. As organizations rely on object storage, managed backups, and provider-controlled retention, courts increasingly scrutinize how cloud-stored evidence is authenticated, preserved, and explained by experts. [1]

Cloud Storage Forensics Is an Expert Testimony Problem

Cloud storage is often discussed as a technical or security challenge. In litigation and regulatory proceedings, it is fundamentally a challenge of expert testimony.

Unlike traditional media, cloud storage provides evidence:

• Is abstracted from physical hardware
• Collected using different mechanisms and tools that do not perform the same way as traditional preservation tools.
• It is often collected from a live environment, making it difficult, if not impossible, to validate the entire collection (“image”) using hashes.
• May contain metadata that is impacted by the Cloud storage services and may not be consistent with standard file metadata from an isolated physical source.

As a result, expert witnesses are no longer testifying solely about what the evidence shows, but about:

• How the storage system functions
• How the extraction process was accomplished
• What the examiner could and could not control
• Where evidentiary uncertainty may exist

LCG perspective. In cloud storage cases, credibility hinges less on tool output and more on whether the expert can clearly explain system behavior, limitations, and dependencies without overstating certainty.

Object Storage and the Reframing of “Original Evidence”

Cloud storage platforms predominantly rely on object storage rather than block-based disks. This distinction directly affects expert testimony.

In object storage systems:

• There is no examiner-verifiable “original disk.”
• Files are reconstructed dynamically from distributed objects
• Metadata and access logs are often more probative than content
• Versioning and lifecycle rules can alter evidence post-creation

Experts must be prepared to explain that:

• An exported file is a logical representation, not a physical artifact
• Multiple valid versions of the same object may exist
• Deletion does not necessarily mean destruction
• Files may originate from cloud storage, but have been created elsewhere

NIST guidance emphasizes that forensic conclusions must account for how systems store and manage data, not merely what data is retrieved. Failure to explain the mechanics of object storage invites admissibility challenges. [2]

Storage Access Logs as Testimonial Evidence

In many cloud storage matters, logs become the primary evidence, not the stored files.

Common expert opinions rely on:

• API access records
• Authentication context
• IP address and token usage
• Timestamps generated by provider systems

However, these logs are:

• Generated by shared, multi-tenant platforms
• Retention-limited and configurable
• May be turned on or off by administrative choice
• Are account licensing dependent (the level of account may dictate the level and duration of logging)
• It may be difficult to obtain without subpoena authority

Under ISO/IEC 27037, evidence handling must be traceable and repeatable. When experts rely on provider-generated logs, they must explain:

• How the logs were created and how they were obtained
• What gaps may exist
• Why the logs are reliable despite the examiner’s lack of control?

This explanation is essential to withstand scrutiny under evidentiary rules. [3]

Chain of Custody Without Physical Custody

Traditional forensic testimony assumes that the chain of custody flows from physical possession. Cloud storage breaks this assumption.

In cloud cases:

• Examiners do not seize storage media
• Providers control replication, redundancy, and backend access
• Evidence preservation often depends on provider attestations

Experts must therefore testify to a logical chain of custody, documenting:

• When preservation was requested, and how it was accomplished
• What controls were applied
• What actions were taken by the provider (if any)
• What verification mechanisms were available

Courts increasingly accept custody maintained by cloud providers, but only when the limits of that custody are clearly disclosed and explained. Claims that data is complete or cannot be changed, without a supporting explanation, are a common reason these efforts fail. [5]

FRE 901: Authentication of Cloud Storage Evidence

Federal Rule of Evidence 901 requires sufficient evidence that an item is what the proponent claims it is.

For cloud storage evidence, authentication challenges often include:

• Logs created outside the organization
• Files exported rather than imaged
• Metadata generated by automated systems
• Lack of examiner access to the underlying infrastructure

Experts must be prepared to authenticate cloud evidence by explaining:

• The regular operation of the storage system
• How records are routinely created and maintained
• Why the evidence has not been altered in a material way

Courts have consistently held that system-generated records may be authenticated through knowledgeable testimony, but only when the witness understands and can explain the system. [7]

FRE 702: Reliability and Expert Opinion Limits

Rule 702 poses a significant challenge to forensic testimony about cloud storage.

Challenges frequently focus on whether:

• The expert used a reliable and repeatable method
• Assumptions about how the cloud provider’s systems work are reasonable and supported
• The conclusions go beyond what the evidence actually shows
• Other possible explanations were identified and addressed

NIST’s forensic science foundation review emphasizes that experts must clearly distinguish between what they directly observed and what they inferred. In cloud storage matters, this distinction is especially important because much of the provider’s system behavior is not visible to the examiner, and the technology behind the cloud storage may be proprietary and unknown.

LCG Perspective:  The risk under Rule 702 is not that cloud forensics is inherently unreliable, but that overstatement is easy when provider systems are partially opaque. Courts tend to reject testimony not because the methodology is unsound, but because the expert fails to clearly label assumptions as assumptions.

Jurisdiction and Expert Disclosure Obligations

Cloud storage evidence often crosses borders automatically.

Experts may be questioned about:

• Where data was actually stored or replicated (physical location of storage server)
• Which jurisdiction’s laws applied (may be multiple)
• Whether access violated data protection standards

EU regulators have emphasized that cross-border data handling, including investigative access, must be legally justified and proportionate. Experts who ignore jurisdictional context risk undermining both admissibility and regulatory compliance. [4]

Examiner-Centered Controls That Strengthen Testimony

1. System-Level Familiarity

Experts must understand storage architecture, retention policies, and logging behavior, not just forensic tools.

2. Transparent Limitation Disclosure

Clearly document what could not be verified, preserved, or controlled.

3. Early Log Preservation

Access logs should be preserved immediately and independently of content exports.

4. Provider Interaction Documentation

All provider involvement should be recorded and disclosed.

These practices align with NIST guidance and strengthen both technical defensibility and courtroom credibility. [2][6]

Why Cloud Storage Forensics Is a Governance Issue

Expert testimony failures in cloud storage cases rarely stem from a lack of skill. They stem from:

• Storage systems adopted without forensic impact analysis
• Retention policies optimized for cost, not evidence
• Contracts are silent on investigative support
• Lack of coordination between legal, IT, and security

By the time an expert is retained, many evidentiary outcomes are already determined.

Quick Checklist

1. Understand that cloud storage artifacts are governed by provider policies
2. Preserve and explain logs as primary evidence
3. Align expert conclusions explicitly with FRE 901 and FRE 702

Final Thought

In 2026, cloud storage evidence does not fail in court because it is digital. It fails because experts are asked to explain systems they did not design, control, or fully observe.

The future of defensible cloud investigations depends on experts who can articulate not only what the evidence shows, but (at least to some extent) how cloud storage systems work, where their limits lie, and why their conclusions remain reliable despite those constraints.

References (endnotes)

[1] LCG Discovery. Forensics and Futures 2026 Series Outline. Internal planning document.

[2] National Institute of Standards and Technology (NIST). SP 800-86: Guide to Integrating Forensic Techniques into Incident Response.
https://csrc.nist.gov/pubs/sp/800/86/final

[3] International Organization for Standardization (ISO). ISO/IEC 27037:2012 – Guidelines for identification, collection, acquisition, and preservation of digital evidence.
https://www.iso.org/standard/44381.html

[4] European Data Protection Board (EDPB). Guidelines 05/2021 on the Interplay between the Application of Article 3 and the Provisions on International Transfers as per Chapter V of the GDPR.
Official EDPB landing page:
https://www.edpb.europa.eu/our-work-tools/our-documents/guidelines/guidelines-052021-interplay-between-application-article-3-and-provisions-international-transfers_en

Direct PDF (authoritative version adopted 18 November 2021):
https://edpb.europa.eu/system/files/2021-11/edpb_guidelines_052021_interplay_between_art3_chapter_v_en.pdf

[5] U.S. Department of Justice, Criminal Division, Computer Crime and Intellectual Property Section (CCIPS). Searching and Seizing Computers and Obtaining Electronic Evidence in Criminal Investigations.
https://www.justice.gov/criminal/cybercrime/docs/ssmanual2009.pdf

[6] National Institute of Standards and Technology (NIST). IR 8354: Digital Investigation Techniques – A NIST Scientific Foundation Review.
https://nvlpubs.nist.gov/nistpubs/ir/2022/NIST.IR.8354.pdf

[7] Legal Information Institute, Cornell Law School. Federal Rules of Evidence, Rule 901 – Authenticating or Identifying Evidence.
https://www.law.cornell.edu/rules/fre/rule_901

[8] Legal Information Institute, Cornell Law School. Federal Rules of Evidence, Rule 702 – Testimony by Expert Witnesses.
https://www.law.cornell.edu/rules/fre/rule_702