Nullity of Proceedings in Criminal Procedure: When It Can Be Requested

Nullity of proceedings in criminal procedure: when it can be requested

One of the fundamental pillars of the rule of law is that the prosecution of crime cannot be carried out at any cost. Criminal proceedings are not a race in which the end justifies the means: the authorities responsible for investigating and prosecuting must scrupulously respect the fundamental rights of citizens, and when that respect fails, the legal system provides a corrective mechanism of enormous importance: the nullity of proceedings.

The nullity of proceedings in criminal procedure is the declaration that certain procedural acts, evidence or measures lack legal validity because they have been carried out in violation of fundamental rights or in breach of essential requirements established by law. Its consequences can be devastating for the prosecution: evidence declared null cannot be assessed by the court, and if that evidence was the basis of the case, its exclusion from the proceedings can directly lead to the acquittal of the defendant.

However, nullity is not an unlimited remedy nor can it be invoked in response to any irregularity. It has precise requirements, specific deadlines and legal limits that determine when it can be requested and with what likelihood of success. Knowing it in depth is one of the most powerful tools of criminal defence, and identifying a nullity in time can completely change the outcome of a case.

In this article we explain what nullity of proceedings in criminal procedure is, what its most frequent causes are, at what moment it can be requested, what effects it produces and what role the defence lawyer plays in detecting and invoking it.

What is nullity of proceedings in criminal procedure?

Nullity of proceedings is the legal sanction established by the legal system for those procedural acts that have been carried out in violation of essential procedural rules or, more seriously, in violation of fundamental rights guaranteed by the Constitution. When a procedural act is declared null, it is deemed not to have been carried out: it produces no legal effect and cannot be used as the basis for any judicial decision.

In criminal proceedings, nullity operates mainly in two closely related areas. The first is that of unlawful evidence, that is, evidence obtained through the violation of fundamental rights such as the inviolability of the home, the secrecy of communications, the right to privacy or the right not to testify against oneself. The second is that of defective procedural acts, those that have been carried out omitting essential formal requirements or without the guarantees that the law establishes for their validity.

The legal basis of nullity of proceedings in Spain is found mainly in Articles 238 and following of the Organic Law of the Judiciary and in Article 11.1 of the same law, which expressly establishes that evidence obtained, directly or indirectly, in violation of fundamental rights or freedoms shall have no effect. This provision, which incorporates into Spanish law the doctrine of the “fruit of the poisonous tree”, is the basis upon which much of the defence strategy in matters of nullity is built.

The poisonous tree doctrine: nullity extends to what derives from unlawful evidence

One of the most relevant principles in matters of evidentiary nullity is what jurists call the doctrine of the fruits of the poisonous tree, taken from North American law and fully integrated into the Spanish legal system. This doctrine establishes that nullity is not limited to evidence directly obtained unlawfully: it also extends to all evidence derived from it, even if this secondary evidence has been obtained in formal compliance with the rules.

The clearest example is the following: if the police enter a home without judicial authorisation and without the consent of the occupant —violating the fundamental right to the inviolability of the home— and there they find incriminating documents, those documents are null. But if, based on those documents, information is obtained that leads to the discovery of a bank account, that account and its contents are also null by derivation. The tree is poisoned at the root, and its fruits —no matter how healthy they may appear— are equally contaminated.

This doctrine has an extremely important practical consequence for the defence: it is not enough to identify the directly unlawful evidence, but the lawyer must trace the entire evidentiary chain to determine what other evidence depends on it and could be dragged down by the nullity. A rigorous analysis of this chain may reveal that the prosecution’s evidentiary framework is much weaker than it appears at first glance.

Most frequent causes of nullity in criminal proceedings

The causes that most frequently give rise to requests for nullity of proceedings in Spanish criminal procedure are the following:

Entry and search of a home without judicial authorisation

The inviolability of the home is one of the fundamental rights most strongly protected by the Constitution. No police officer may enter a person’s home without their express consent or without prior judicial authorisation, except in the case of flagrante delicto. When a search is carried out without these requirements, everything obtained during that search is null, including documents, objects or substances that may have been found, as well as any evidence derived from the discovery.

Defects in the judicial authorisation may also lead to nullity: if the order authorising the search is not sufficiently reasoned, if the search is carried out outside the authorised scope or time, or if the procedural guarantees established for its execution are not complied with —presence of the interested party or a relative, drafting of a record— the result may be equally invalid.

Interception of communications without guarantees

The interception of telephone, electronic or postal communications is one of the most intrusive investigative measures and, for that reason, the one that requires the most and strictest requirements. It can only be ordered by means of a reasoned judicial decision, which must precisely identify the numbers or accounts subject to interception, the offences under investigation, the duration period and the control mechanisms. If any of these essential requirements is missing, or if the interception continues beyond the authorised period without judicial renewal, the content of the intercepted communications is null and cannot be assessed by the court.

In recent years, the emergence of new forms of digital communication —WhatsApp, emails, encrypted messaging— has raised new questions regarding the requirements necessary to legitimately intercept such communications. The case law of the Supreme Court and the Constitutional Court has been establishing specific criteria for each modality, and the failure to comply with those criteria is a frequent source of nullities in the most recent criminal proceedings.

Statements obtained without guarantees or under coercion

Statements by the suspect, the defendant or witnesses must be obtained in strict compliance with the guarantees established by law. In the case of the suspect, no statement may be obtained without prior information of their rights: the right to remain silent, the right not to testify against oneself, the right to legal assistance. A statement given without that prior information, or without the presence of a lawyer when required, may be declared null.

Equally null are statements obtained through coercion, threats, deception or any form of undue pressure on the declarant. The prohibition of torture and of inhuman or degrading treatment is absolute in our legal system, and any statement obtained under such conditions is not only null but may also give rise to additional criminal liability for those who carried it out.

Expert evidence without procedural guarantees

Expert reports may also be subject to nullity when they have been obtained or carried out without complying with the procedural requirements established by law. Failure to summon the suspect for the performance of the expert examination, lack of notification that prevents the defence from proposing its own expert, or the practice of expert evidence without ensuring the necessary adversarial principle may lead to its nullity. Likewise, reports prepared by experts who are in a conflict of interest or who clearly exceed the scope of their specialisation may be challenged with real prospects of success.

Violation of the right of defence during the investigation stage

The violation of the right of defence during the investigation phase may give rise to the nullity of the affected proceedings. This includes situations such as carrying out measures without notifying the suspect when such notification was required, unjustified denial of investigative measures requested by the defence, the suspect’s statement without the presence of their lawyer when this was necessary, or the unjustified maintenance of secrecy of the proceedings beyond the legal deadlines. In all these cases, the defence must articulate the nullity precisely and with grounds, indicating exactly which act is null, for what reason and what procedural consequences that nullity must have.

When and how can nullity of proceedings be requested?

Nullity of proceedings can be requested at different stages of the process, and the chosen timing may influence the chances of success and the effects it produces:

During the investigation phase

When the defence lawyer detects an irregularity during the investigation —for example, that a search has been carried out without judicial authorisation or that communications have been intercepted without complying with legal requirements— they may request nullity within the investigation proceedings themselves through the appropriate appeal against the decision that ordered the irregular measure. Acting at this stage is particularly effective because it allows the tainted evidence to be excluded before it contaminates the rest of the proceedings and before the entire prosecutorial structure is built upon it.

In the intermediate phase and in the defence statement

If the nullity was not alleged during the investigation —or could not be because the irregularity was not known until that moment— it may be raised in the intermediate phase through the defence statement. In this document, the lawyer may identify the evidence considered unlawfully obtained, argue legally why it is null and request that it be excluded from the proceedings before the trial begins. This is the most orderly and least risky way to channel the claim of nullity.

At the beginning of the trial as a preliminary issue

At the start of the trial, before any evidence is taken, the parties may raise preliminary issues including the request for nullity of certain acts or evidence. If the court upholds the nullity at this moment, the affected evidence is excluded from the trial and the court cannot assess it. If it rejects it, the defence may lodge a protest to preserve its right to invoke nullity as a ground for appeal against the judgment.

On appeal against the judgment

If the nullity was not upheld during the trial —or if it was not raised at that moment— it may be invoked as a ground for appeal against the conviction before a higher court. In this case, the appellate or cassation court analyses whether the nullity should have been upheld and, if it upholds it, it may annul the judgment and order a retrial without the tainted evidence, or even directly issue an acquittal if the null evidence was the only basis of the conviction.

Limits and nuances of nullity: not every irregularity leads to it

It is important not to fall into the mistake of thinking that any procedural irregularity, however minor, automatically leads to nullity. The legal system distinguishes between invalidating irregularities —those that affect fundamental rights or essential procedural guarantees and that do produce nullity— and remediable or merely formal irregularities, which do not have that effect.

The Constitutional Court and the Supreme Court have developed over the years detailed case law on what types of irregularities produce nullity and which do not. In general terms, nullity requires that the irregularity has caused real and effective defencelessness, that is, that it has deprived the defendant of the possibility of exercising their defence in such a way that the outcome of the process could have been different if the irregularity had not occurred. Purely formal irregularities that have not caused any real harm to the defence generally do not lead to nullity.

This requirement of real defencelessness has an important practical implication: when nullity is alleged, it is not enough to point out that an irregularity has occurred. It is also necessary to argue what specific harm that irregularity has caused to the right of defence and how it may have influenced the outcome of the process. A lawyer who alleges nullities without substantiating the harm caused has little chance of success.

The role of the defence lawyer in detecting and invoking nullities

Nullity of proceedings is, in many cases, the most powerful tool of criminal defence. But to use it effectively it is essential to have a criminal lawyer with the technical knowledge necessary to identify irregularities, the experience to know which ones are truly invalidating and the procedural skill to articulate them at the right moment and in the correct manner.

The detection of possible nullities requires an exhaustive and meticulous analysis of the case file: reviewing each order that authorised investigative measures, verifying that judicial authorisations comply with all legal requirements, checking that notifications were properly carried out, analysing whether statements were obtained with all guarantees and tracing the evidentiary chain to identify which evidence depends on others that may be null.

This analysis must begin from the very moment the lawyer assumes the defence, not when the trial is about to be held. Nullities that are not detected in time, or that are not invoked at the appropriate procedural moment, may be lost forever. In some cases, the inaction of the defence may be interpreted as an implicit waiver of invoking nullity, which underscores the importance of acting diligently and with proper legal advice from the beginning of the process.

Frequently asked questions

Does the nullity of evidence automatically imply the acquittal of the defendant?
Not necessarily. The nullity of evidence implies that such evidence must be excluded from the proceedings and that the court cannot assess it. But if the prosecution has other valid and independent evidence that is sufficient to prove the defendant’s guilt beyond reasonable doubt, the court may still convict on the basis of that other evidence. Acquittal will only be the inevitable result when the null evidence was the only or main support of the accusation and without it there is no sufficient evidentiary basis to sustain the conviction.

Can the court declare nullity ex officio without the defence requesting it?
Yes. When the violation is so serious that it clearly affects fundamental rights, the court may declare nullity ex officio, that is, without any of the parties having expressly requested it. This possibility exists because the protection of fundamental rights is not an issue that concerns only the parties to the process: it is a requirement of the rule of law itself that the judge is obliged to safeguard independently of the parties’ requests. Nevertheless, in practice, it is much more common for nullity to be declared at the request of the defence than ex officio by the court.

What happens to the proceedings if nullity is declared?
The consequences depend on the scope of the nullity. If it only affects one or several specific pieces of evidence, the process continues without them and the court must rule on the defendant’s guilt on the basis of the evidence that is valid. If the nullity is of such magnitude that it affects essential procedural acts —such as the suspect’s statement taken without due guarantees— it may lead to the proceedings being rolled back to the moment when the irregularity occurred, so that that act can be repeated correctly. And if the nullity affects elements so fundamental that the process cannot continue, it may lead to the dismissal of the proceedings.

Can nullity be requested even if the trial has already ended and there is a conviction?
Yes, although with more limited scope. If nullity was not upheld during the process, it may be invoked as a ground for appeal or cassation against the conviction. If it was not upheld in those instances either and the judgment is already final, the path is much narrower: only an amparo appeal before the Constitutional Court may be useful if the nullity is based on a violation of a fundamental right recognised in the Constitution, and provided that all ordinary judicial remedies have previously been exhausted.

Can nullity be used as a delaying tactic to slow down the process?
Nullity of proceedings is a tool for the protection of fundamental rights, not an instrument to delay the process fraudulently. Courts are increasingly demanding in the substantiation of nullity requests, and manifestly unfounded allegations of nullity or those raised for purely obstructive purposes may be rejected outright and may even lead to negative consequences for the party raising them. Nullity must be invoked when there is a solid legal basis and real harm to the right of defence, not as a tactic of attrition. A responsible and discerning lawyer only invokes it when there is a real basis to do so.