Blockchain Forensics in the Courtroom: Giving Expert Evidence on Digital Asset Disputes

Digital asset disputes have become an established feature of litigation. Exchange insolvencies, wallet compromises, smart contract exploits, algorithmic trading failures, and fraud recovery actions have all generated litigation in England and Wales over the past several years. With them has come a class of technical evidence that presents particular challenges: blockchain forensic evidence.

The analysis required in these matters draws on disciplines that do not map neatly onto traditional digital forensics. An expert instructed on a blockchain dispute will need to work simultaneously with publicly accessible on-chain data, proprietary exchange records, software source code, and, in some cases, cryptographic key material. Each of these carries different evidential weight, different preservation requirements, and different explanatory challenges when the matter reaches a tribunal.

Having given expert evidence in proceedings involving digital asset disputes and trading system analysis, I set out below how blockchain forensic evidence is prepared and presented, what on-chain analysis can and cannot establish, and what solicitors and in-house counsel should consider when instructing a technical expert in this area.

How blockchain evidence differs from traditional digital forensics

Conventional digital forensics is principally concerned with device-level artefacts: files recovered from storage media, application logs, metadata extracted from documents, and communications data obtained from platforms. The focus is on what a device or system recorded, and whether that record is authentic and complete.

Blockchain evidence operates differently. A public blockchain such as Bitcoin or Ethereum is a distributed ledger, replicated across thousands of independent nodes. Every transaction broadcast to the network and included in a confirmed block is, in principle, permanently and publicly accessible. There is no single custodian of the record, and the data is not held on any device under a party’s control. This creates both strengths and limitations that have no direct equivalent in conventional forensics.

The principal strength is immutability. A transaction confirmed to sufficient depth on a major public blockchain cannot, under normal circumstances, be altered or deleted. The record is not subject to the same tampering risks as a log file on a corporate server. For the purposes of tracing asset movements, the on-chain record provides a complete and ordered history from the moment a wallet receives funds to the moment those funds are transferred onward.

The principal limitation is that on-chain data records what happened at the protocol level, not who caused it to happen. A transaction records the sending address, the receiving address, the amount transferred, the timestamp, and the transaction fee. It does not record the identity of the individual who authorised it, the device from which it was broadcast, or the circumstances in which the private key was used. Bridging the gap between an on-chain event and a named individual requires additional evidence, and that step can be where disputes are most keenly contested.

Off-chain evidence, meaning records held by exchanges, custodians, wallet software providers, and other intermediaries, carries more direct probative value for questions of identity and intent in many cases. KYC records, login timestamps, IP addresses, withdrawal confirmations, and support correspondence are the kinds of materials that connect blockchain activity to a real-world actor. In practice, a thorough blockchain forensic investigation will involve both layers, and the interaction between them matters.

On-chain analysis: transaction tracing and wallet attribution

A core task in many blockchain disputes is following the movement of funds. This involves tracing transactions across multiple wallet addresses, identifying consolidation or dispersal patterns, and attributing clusters of addresses to a common controller where the evidence supports that inference.

Transaction tracing on a public blockchain is, at a technical level, straightforward: every input and output is recorded, and the chain of custody for a given unit of value can be reconstructed by following the transaction graph. The complexity arises from the volume of transactions involved, the use of intermediary addresses, and deliberate obfuscation techniques such as mixing services, chain-hopping across different blockchains, or the use of privacy coins.

Wallet clustering and attribution rely on heuristics derived from how blockchain protocols work in practice. The most well-established of these is the common-input-ownership heuristic: where a transaction combines inputs from multiple addresses, those addresses are likely under common control, because constructing such a transaction requires access to the private keys for each input address. Other heuristics relate to change address identification and behavioural patterns across transactions. These heuristics are probabilistic rather than deterministic, and their application should be explained and qualified in any expert report.

Commercial blockchain analytics tools are widely used in this work. They aggregate attribution data from public sources, proprietary intelligence, and historical analysis to associate wallet addresses with known entities such as exchanges, mixers, or sanctioned actors. The outputs of such tools can assist in establishing the likely destination or origin of funds, but they require scrutiny. The underlying attribution data may be of uncertain provenance, and the tools should not be treated as producing conclusions in their own right. Where such tools are relied upon in an expert report, the basis for the attribution, the confidence level assigned by the tool, and the expert’s independent assessment of that confidence should all be addressed.

What on-chain analysis can establish, subject to appropriate qualification, includes: the sequence and timing of transactions; the amounts transferred; the addresses involved and their clustering; and, where attribution data is reliable, the likely association of an address with a particular service or entity. What it generally cannot establish without corroborating off-chain evidence is the identity of the individual who authorised a specific transaction, the location from which a transaction was broadcast, or the intent behind a particular pattern of activity.

Smart contract and code review

A distinct category of blockchain dispute involves the behaviour of smart contracts or automated trading systems. Smart contracts are programmes deployed to a blockchain that execute automatically when their conditions are met. Their code is typically immutable once deployed, and their execution is deterministic: given the same inputs and state, a smart contract will produce the same outputs.

Disputes in this area may turn on whether a smart contract behaved as its parties intended, whether a vulnerability in the contract code was the cause of a loss, or whether an external actor exploited a weakness in the contract design. These are questions that require source code review and, where the deployed bytecode differs from the available source, decompilation and comparative analysis.

In Terraform Labs Pte Ltd v Wintermute Trading Ltd [2024] EWHC 737 (KB), I provided written expert evidence on source code analysis in the context of a dispute involving cryptocurrency trading code architecture, distinguishing between trading algorithms, execution code, and integration systems. The case illustrates the type of technical examination that arises when the behaviour of a software system is itself in issue: the expert must reconstruct what the code did, assess whether it did what the parties expected, and explain that analysis in terms accessible to a non-technical court.

The specific questions that arise in smart contract review include: whether the deployed contract matches the source code provided by a party; whether the contract contains known vulnerability patterns; how the contract interacted with external data sources or other contracts; and whether the behaviour observed on-chain is consistent with the contract’s documented specification. Each of these questions requires a structured methodology and clear documentation of the steps taken, the tools used, and the basis for any conclusions drawn.

Where a dispute involves proprietary trading code rather than a publicly deployed smart contract, the analysis is closer to conventional software forensics: examining version history, reviewing logs, and assessing whether the system behaved within its design parameters. The expert’s role is to translate the technical record into findings that a court can evaluate, not to advocate for a particular interpretation of that record.

Presenting blockchain evidence to a non-technical tribunal

One of the more demanding aspects of giving expert evidence in digital asset disputes is explaining distributed ledger technology to a judge who may have limited familiarity with the underlying concepts. A transaction hash, a wallet address, a block confirmation, and a consensus mechanism are terms that require explanation before they can be used to build any forensic argument.

In my experience, the most effective approach is to build the explanation from first principles, using analogies that are accurate enough to be helpful without being so simplified as to mislead. A public blockchain can be described as a shared ledger, maintained by a network of independent participants, in which every entry is visible to all participants and cannot be altered once confirmed. A wallet address can be explained as a destination identifier, analogous in function to a bank account number, but without the institutional relationship that the banking analogy might imply. The distinction matters, because unlike a bank account, a wallet address is not inherently tied to an identity.

Diagrams and transaction flow charts are useful tools for presenting transaction tracing evidence. Where funds move through a series of addresses, a visual representation of that movement is generally more accessible than a table of transaction hashes and amounts. The expert report should be drafted on the assumption that the reader has no prior knowledge of how blockchains work, and each technical term should be defined when first used.

Cross-examination in this area may focus on the limits of the analysis. The expert should be prepared to explain, clearly and without defensiveness, what the on-chain data does not show, why attribution to a specific individual requires corroborating evidence, and what assumptions underlie any clustering or tracing conclusions. A report that acknowledges its limitations, and explains them, is more robust under examination than one that states conclusions without qualification.

Evidential considerations

Several evidential questions arise specifically in the context of blockchain forensic evidence, and solicitors should be aware of them when building a case.

Whether on-chain data engages the hearsay rules has not, to my knowledge, been the subject of definitive appellate guidance in England and Wales, and the answer may depend on the nature of the data and how it is relied upon. Transaction records on a public blockchain are generated by the protocol rather than authored by a person in the conventional sense, which places them closer to automatically generated computer records than to statements made by a person. In civil proceedings, hearsay evidence is in any event admissible under the Civil Evidence Act 1995, subject to the notice requirements in CPR Part 33, and the practical questions are more likely to concern weight, authenticity, and completeness. Expert evidence may be used to interpret and contextualise on-chain data rather than simply to introduce it. Solicitors should consider this question early, particularly in cases where the authenticity or completeness of the blockchain record itself may be in issue.

Chain of custody for blockchain evidence requires some care. On-chain data is publicly accessible and does not require seizure from a device, but the process by which it is collected, the tools used, and the version of the data captured at a particular point in time should be documented. Where analysis relies on commercial blockchain analytics platforms, the date on which queries were run and the version of the attribution data used should be recorded, as attribution datasets are updated over time and results may differ if the analysis is repeated at a later date.

Off-chain evidence can be more fragile. Exchange records, wallet software files, private key material, and correspondence held by intermediaries may be subject to deletion, modification, or loss if preservation steps are not taken promptly. Solicitors should consider early preservation requests to relevant exchanges, custodians, and service providers, and should advise clients to preserve any wallet software, seed phrases, hardware wallets, and related documentation without alteration.

Private key material requires particular care. A private key is both evidence and a functional asset: it controls access to funds held at the corresponding wallet address. Instructions regarding the preservation and handling of private key material should be clear, and any transfer or use of keys pending resolution of proceedings should be addressed explicitly.

Practical guidance for solicitors

The following considerations are relevant when instructing a technical expert in a blockchain or digital asset dispute.

Instruct early. Blockchain disputes may involve time-sensitive evidence. Exchange records may be deleted after a retention period, blockchain analytics attribution data may change, and wallet software or devices may be at risk of loss or alteration. An expert instructed at the outset can advise on what to preserve and how.

Define the scope of instructions carefully. Blockchain forensics, smart contract review, and trading system analysis are distinct disciplines, and not every expert in one area will have depth in the others. Instructions should identify whether the dispute turns primarily on fund tracing, contract code behaviour, or system performance, and the expert’s relevant experience should be assessed against the specific technical questions in issue.

Preserve off-chain evidence proactively. On-chain data will generally be recoverable, but exchange records, KYC documentation, login histories, IP logs, support communications, and wallet software files may not be. Early engagement with custodians and service providers, using appropriate legal mechanisms, is advisable where blockchain disputes involve off-chain actors.

Consider the interaction with other forensic disciplines. Blockchain forensics does not stand in isolation in many cases. A wallet compromise case may also involve device forensics to examine how a private key was accessed. A trading system dispute may involve software forensics, log analysis, and network traffic examination alongside smart contract review. The expert’s report should address how the blockchain evidence relates to other evidence in the case, and joint instructions with other technical experts should be considered where the technical issues overlap. The relationship between blockchain forensics and conventional digital evidence examination is particularly relevant where the dispute involves communications or device data alongside on-chain activity.

Plan for tribunal explanation. If the matter is likely to proceed to a hearing, the expert should be briefed on the technical background of the tribunal and should consider what explanatory materials, such as diagrams, glossaries, or worked examples, may assist the court. Preparation of these materials takes time and should be built into the instruction timeline.

Blockchain forensic evidence is technically demanding and continues to evolve as the underlying technology develops. In my experience, the cases in which technical evidence is most effective are those in which the expert has been given sufficient time, clear instructions, and access to the full range of relevant material, both on-chain and off. Early engagement with the technical issues tends to produce better-prepared evidence and a cleaner presentation when the matter reaches court.