In previous articles, the Lucchesi Advocacia Blog examined chain of custody and the validity of digital evidence in depth. The topic dominated doctrinal discussions in 2025 and, in 2026, remains highly relevant.
Despite the growing frequency with which chain of custody violations are raised, the form of the allegation is not always sufficient to exclude evidence or suspend criminal proceedings. This article examines the relationship between alleging a chain of custody violation and its eventual recognition, from two extremes: the bare assertion of nullity, unsupported by argument, and the burden of proving a procedural violation without access to the procedure’s own records.
Digital Evidence and Chain of Custody
Criminal investigations and judicial proceedings increasingly rely on expert reports and digital data analysis. Precisely because of the malleability of digital data, the entire procedure for extracting, maintaining, and documenting trace evidence must be properly recorded.
That record is what guarantees the repeatability and integrity of the evidence: the extraction result must be identical regardless of who performs it, so that the handling itself does not alter the content stored on the digital media.
The Proliferation of the Debate in the Courts
Chain of custody violations have become a recurring issue in cases involving digital evidence. The central question, however, remains open: is the mere allegation of a violation sufficient to invalidate tainted evidence?
The Brazilian Superior Courts point in a uniform direction, even if for distinct reasons. The 5th Panel of the STJ established that a conviction may be upheld even when a chain of custody violation is recognized, provided that independent evidence is sufficient to support it.
In a convergent ruling, the 6th Panel of the STJ held that recognizing a violation does not automatically render the evidence null. For the panel, the challenged evidence must be assessed in the context of the full evidentiary record, leaving it to the judge to determine its reliability.
In short, for Brazil’s Superior Courts, a chain of custody violation does not automatically nullify evidence or strip it of its legal effect. Nor is it sufficient, in isolation, to taint all acts carried out in the proceeding — a conviction may even be upheld, provided it rests on independent evidentiary elements.
A Bare Allegation Is Not Enough
This jurisprudential framework does not resolve the practical problem faced by the defense: if a violation does not automatically generate nullity, what is required to establish it?
As decisions recognizing chain of custody violations have multiplied, so have defensive requests for nullity — but that conclusion does not follow automatically from recognizing the defect, and it is precisely there that many defensive arguments lose force.
Recent decisions from the Superior Courts have established two guiding principles:
- Formal non-compliance with procedure, standing alone, does not automatically establish a chain of custody violation.
- A recognized violation only constitutes procedural nullity when it is shown that the defect compromises the effectiveness of the evidence.
For the argument to succeed, the allegation must be connected to the full evidentiary record and demonstrate, concretely, the harm to the integrity of the material.
The Impossible Proof
Here lies the true practical problem — and the point that technical defense counsel must explore with rigor.
The dominant judicial understanding requires the party to demonstrate how the integrity of the evidence was compromised and what evidence of tampering or harm exists. Without the record of the extraction, maintenance, and documentation procedure, however, that demonstration becomes materially impossible.
The requirement, in the abstract, seems reasonable. The problem arises when it is applied to a scenario in which the very absence of documentation is the alleged defect. Requiring the defense to prove tampering without access to the procedure’s records amounts to imposing a burden of proof that is impossible to discharge — which directly undermines the equality of arms in criminal proceedings.
This reasoning carries even more weight when the evidence is exclusively digital — with no documentary counterproof, no witnesses to the procedure, and no accessible extraction report. In such cases, the evidentiary record does not fill the gap left by the absence of documentation, and the compromise to the evidence’s effectiveness is structural, not merely formal.
The central point, therefore, is not to prove that tampering occurred. It is to demonstrate that, given the absence of records, the reliability of the examined material cannot be verified — and that this impossibility of verification, in itself, undermines the validity of the evidence as the basis for a conviction.
Conclusion
The debate over chain of custody violations reveals a structural tension in Brazilian criminal procedure: the State that produces the evidence is the same entity that should guarantee the conditions for verifying its integrity, repeatability, and identity — and frequently does not.
The Superior Courts are right to refuse automatic recognition of any alleged violation, since an allegation unsupported by concrete demonstration of harm is insufficient to invalidate the evidence.
Yet a critical question remains open: when the absence of documentation is the very defect at issue, shifting to the defense the burden of proving tampering means imposing an obligation the State has made impossible to fulfill.
Technical defense counsel, therefore, must not limit itself to alleging a formal violation. The precise argument is different: without documentation of the procedure, the reliability of the examined material cannot be assessed — and evidence whose reliability cannot be verified does not meet the conditions to sustain a conviction.
This argumentative shift — from formal nullity to evidentiary inefficacy through impossibility of verification — is what distinguishes a generic allegation from a consistent defensive theory.
Schedule a legal consultation with Lucchesi Advocacia for technical guidance on digital evidence and criminal defense strategy.
