Crypto-Assets and the Chain of Custody of Evidence

Abstract

The growth of the crypto-asset market and its widespread adoption in Brazil have placed these assets at the center of judicial proceedings, particularly in asset recovery. Even so, there is still no consolidated theory on the evidentiary treatment of crypto-related evidence. This article examines how the chain of custody, governed by Articles 158-A to 158-F of the Brazilian Code of Criminal Procedure, applies to evidence involving crypto-assets. Its theoretical framework is the rationalist conception of evidence. The article argues that the chain of custody concerns the reliability of evidence, not its admissibility. Consequently, failure to comply with it does not render the evidence null and should instead be taken into account in the assessment of the evidence. The central thesis is that crypto-asset evidence is not a unitary category: each type raises its own epistemic and legal problems, and the types differ in how far the data can stand on its own without external verification mechanisms. Data recorded on sufficiently decentralized public blockchains is self-authenticating through simple public verification, so the chain-of-custody framework does not apply. For data provided by centralized virtual asset service providers (VASPs), reliability depends on the institutional trustworthiness of the source and on how the data is received and preserved. For blockchain intelligence tools, address clustering requires methodological validation of the heuristic used. Attributing those addresses to real-world entities, in turn, depends on off-chain evidence, each piece subject to its own custody regime. Finally, when crypto-asset data is linked to other digital evidence, the chain of custody applies in full and requires additional safeguards in handling private keys and recovery phrases (seed phrases).