WhatsApp Witness Statements: Validity and Limits Under Spanish Case Law

The growing use of digital tools in judicial practice has raised questions about the validity of evidence obtained through non-traditional means. One of the most common in recent years is the witness statement taken via video call in messaging applications. In its ruling of 12 March 2026 (appeal 5149/2023), the Spanish Supreme Court set clear criteria for when a statement taken via a WhatsApp video call may validly be assessed as evidence in criminal proceedings.

The general principle: formal irregularity does not equal nullity

The starting point of the ruling is the general principle that purely formal irregularities do not invalidate evidence if they do not affect basic procedural principles. This criterion is not new: the Supreme Court has applied it repeatedly in relation to the interception of communications, searches and expert evidence. Extending it to witness statements taken by digital means is the ruling's most significant contribution.

The LECrim regulates witness statements by videoconference in Article 731 bis (in conjunction with Article 229 LOPJ) and does not prohibit the use of other equivalent technical means where there are reasons to justify them. The absence of explicit regulation does not mean prohibition: it means that the method adopted must respect the principles that give any testimony its validity.

The criteria for the validity of a remote statement

For a WhatsApp witness statement to survive judicial scrutiny, the ruling requires three elements to be verified.

First, the identity of the witness. The assurance that the person testifying is who they claim to be is indispensable. In the case resolved, the witness's identity was treated as notorious and was not challenged by any of the parties. That lack of challenge has procedural consequences: a party that does not question identity at the appropriate moment will find it very difficult to do so successfully afterwards.

Second, the perception of credibility. The court must have been able to observe the witness's gestures, attitude and the spontaneity of their answers in order to assess whether they were testifying according to their real knowledge of the facts. Video technology allows, within the limitations of the medium, that direct perception. Where the medium makes that observation entirely impossible, the problem ceases to be purely formal.

Third, the effectiveness of adversarial examination. The parties must have had a real opportunity to question the witness and to put the questions they considered relevant. If the mode of testimony effectively prevented that right from being exercised, the irregularity goes beyond the purely formal and may lead to nullity.

Actual defencelessness, not merely formal

The ruling insists that not every procedural irregularity gives rise to constitutional defencelessness. For an irregularity in the taking of witness evidence to justify exclusion, the party invoking it must show that it caused actual, not merely formal, defencelessness. This means demonstrating, first, that the irregularity occurred; second, that it deprived the party of a specific procedural opportunity; and third, that that deprivation influenced the outcome of the evidence to the party's detriment.

This requirement is consistent with the Constitutional Court's case law on the right to evidence under Article 24.2 of the Spanish Constitution: constitutional protection of that right does not extend to procedural breaches that have not produced effective harm to the party's procedural position.

Challenge from the defence perspective

For the defence, the judgment provides a clear map of the arguments that may succeed and those that will not. A challenge based solely on the medium used will not succeed: arguing that a statement was taken by WhatsApp without connecting that fact to a concrete breach of one of the basic procedural principles is insufficient.

A challenge may succeed where it is shown that the witness's identity was not verified with sufficient certainty, that the quality of the connection prevented the credibility indicators from being perceived, or that the technical conditions of the statement obstructed the effective right to cross-examine. In those situations the formal irregularity becomes a real breach of the right to evidence and may lead to the nullity of the statement and, with it, the exclusion of the evidence obtained.

The prosecution and court perspective

For the party supporting the validity of the evidence — both the prosecution and the court — the ruling allows reliance on the fact that a failure to object at the right time limits the prospects of a later challenge. If the party against whom the evidence is directed did not question the witness's identity, did not request additional identification safeguards and did not object to the technical conditions of the statement, the door to a later challenge becomes considerably narrower.

The ruling is also a call to courts conducting pre-trial investigations to record, when they resort to remote means of testimony, the reasons justifying that decision, the steps taken to verify the witness's identity and the conditions in which the procedure was carried out. That documentation reinforces the validity of the evidence and makes it harder to challenge afterwards.

Practical implications in criminal proceedings

The doctrine set by the Supreme Court applies beyond the specific case of WhatsApp: it extends to any mode of witness testimony taken by remote technical means — videoconference, other messaging systems, statements taken abroad — where the validity of the evidence obtained is at issue.

The ruling reinforces the idea that criminal proceedings must adapt to technological reality without abandoning essential guarantees. Physical presence has ceased to be the only admissible form of witness testimony; what remains non-negotiable is that the court must be able to perceive the witness, that the parties must be able to question them and that the person testifying must be properly identified. Beyond those requirements, an irregularity in the medium does not by itself determine the nullity of the statement.