Pre-trial detention and secret proceedings: the defence must know the essential evidence

The facts and the Constitutional Court's decision

Spanish Constitutional Court Judgment 15/2026 decided an amparo application brought by a person arrested on 30 January 2025 in a secret investigation into an alleged organisation involved in trafficking cannabis resin. Before the detention hearing, the investigating court gave him a summary that referred to recorded conversations and other technological investigative measures, but did not provide their specific content.

The defence expressly requested access to the telephone conversation linking the suspect to the alleged offences. The investigating court refused the request, ordered pre-trial detention on 2 February 2025 and confirmed the measure on the 14th. The Criminal Chamber of the National Court subsequently dismissed the appeal.

The Constitutional Court granted amparo for breach of the rights to personal liberty and defence under Articles 17(1) and 24(2) of the Spanish Constitution. It annulled the three orders because the conversation was the principal item of evidence used to justify detention, yet neither its recording nor a transcript had been provided. The applicant had already been free since 19 December 2025, so the ruling had declaratory effect and did not order a further release.

Secrecy does not permit information devoid of substance

Article 302 of the Spanish Criminal Procedure Act allows proceedings to be declared wholly or partly secret when necessary to protect a person or prevent serious harm to the investigation. Article 505(3), however, gives the lawyer access in every case to the essential elements needed to challenge the deprivation of liberty.

The judgment distinguishes between disclosing the entire case file and enabling an effective defence against detention. There is no automatic right to know every secret investigative step. The essential source must nevertheless be identified and its content provided when it connects the alleged events with the person whose detention is sought.

It is therefore not enough to state that there are ‘intercepted conversations’ or ‘technological investigations’. If a call is the decisive item of evidence, the defence must be able to know the relevant conversation through a recording or transcript. If the court considers that requested material is not essential, it must give individual reasons; a general reference to risk to the investigation is insufficient.

What the defence may request and when

Access is not always granted of the court's own motion: the defence must request it expressly and specifically. It may do so before or during the Article 505 hearing, when appealing the detention order or when later seeking its review. The safeguard continues for as long as the person remains in pre-trial detention.

Depending on the case, essential material may include a complaint, incriminating statements, expert reports, documents, photographs, videos, search records or data obtained through telephone interception and other technological measures. What matters is not the label attached to the investigative step, but whether it was actually used to support the provisional inference of involvement and the need for detention.

The request should identify the material, explain why it is decisive and seek a form of access compatible with protecting the investigation. It is also advisable to record both the request and the response so that an appeal can be properly supported. A general request for the whole case file may be less effective than identifying the conversation, report or record on which the measure rests.

Practical implications of Spanish Constitutional Court Judgment 15/2026

For the suspect, this doctrine makes it possible to compare the actual content of evidence with the summary provided, offer an alternative explanation and dispute the strength of the indication. It does not mean that all pre-trial detention in secret proceedings must be lifted: the measure may remain in place when its legal requirements are met and these safeguards are respected.

For the prosecution and the court, the judgment requires them to define what material is essential and give reasons for any restriction. Information unrelated to the detention decision, or whose disclosure would create a specific risk, may be protected; the content of the evidence used to deprive a person of liberty cannot be withheld while the defence is expected to rebut it.

Annulment of a detention order is not an acquittal either. The investigation may continue, and criminal liability will be decided on the evidence validly admitted in the proceedings. The issue decided by the Constitutional Court was whether detention had been ordered in compliance with fundamental rights, not whether the alleged offences were committed.

Criminal-law advice in Tenerife

If you or a family member face a detention hearing, secret criminal proceedings or a review of a precautionary measure, the firm can examine the material supporting the request, make a specific application for access and prepare the challenge within the applicable time limits.

You can request a consultation with Abogado Juan in Santa Cruz de Tenerife, by phone or video call. This content is informational, comments on a specific judgment, does not replace individual legal advice and does not predict the outcome of any proceedings.