Is it legal to hire a private investigator in Spain? Yes: investigating to defend your rights is protected by law
Even today, some clients arrive at our first meeting with a certain wariness: "Can this be done?", "Is it legal to investigate another person?", "Will I be able to use what I find out afterwards?"
The answer, when there is a legitimate interest and the service is carried out by a licensed investigator within the limits of the law, is unequivocal: yes.
Hiring a private investigator is an activity expressly provided for and regulated by Spanish law. This is not a grey area, nor an activity that is merely tolerated.
And there is an even more important dimension: when the investigation is aimed at obtaining the facts and evidence needed to assert a right before a court, the investigator's activity connects directly with the fundamental right to use the evidence relevant to one's defence.
The law doesn't tolerate the investigator: it regulates them
The Private Security Act (Law 5/2014) devotes a chapter to the services provided by private investigation agencies.
Its Article 48 defines these services as the inquiries necessary to obtain and provide, on behalf of legitimately entitled third parties, information and evidence on private conduct or facts.
And it establishes the fields of action: economic, employment-related, commercial, financial, personal, family or social, and, under certain conditions, the investigation of offences prosecutable only at the request of a party.
The law uses two essential words: information and evidence.
The investigator is not simply someone who finds things out. They are the professional whom the legislator licenses to investigate private facts and turn the outcome into material capable of being used to defend legitimate interests.
The right to resort to private services
The preamble of Law 5/2014 refers to citizens' right to create or use private security services and to their contribution to the protection of legitimate rights and interests.
Private investigation is part of that system.
The Third Chamber of the Supreme Court, in its ruling of 19 February 2008, explained that the legislator had unified private investigation in the figure of the private investigator.
In certain fields of private investigation, therefore, we are dealing with the professional figure specifically licensed by law to carry out that activity.
When there is a court proceeding, Article 24 of the Constitution comes into play
Article 24.2 of the Constitution recognises every person's right to use the evidence relevant to their defence.
Being right and being able to prove it are two different things.
A business owner may know they are the victim of unfair competition. A parent may know that the person obliged to pay maintenance is concealing their true economic activity. A company may suspect internal fraud. But a court does not rule on hunches: it rules on established facts.
That is where an essential function of the investigator comes in: transforming a legitimate suspicion into facts capable of being proven.
The Constitution does not contain a supposed "fundamental right to hire investigators." It doesn't need to. What matters is that it recognises a fundamental right to evidence, and that the legislator has specifically regulated a profession capable of obtaining and providing certain kinds of private evidence.
When a person legitimately turns to an investigator to obtain the evidence needed to defend their rights, private investigation can become an instrument for the effective exercise of Article 24 of the Constitution.
Strasbourg: defending a right requires being able to obtain evidence
In Köpke v. Germany (2010), the ECtHR examined covert surveillance carried out with the involvement of a private investigation agency amid suspicions of theft at a supermarket.
The Court took into account the measure's temporal and spatial limits, its specific purpose, and the restricted use of the data, and weighed the employer's interest in protecting its property and obtaining evidence for the courts.
The idea is fundamental: privacy is a legally protected interest, but so is the ability to prove before a court that a right has been infringed.
The Spanish Supreme Court: STS 851/2021
A former wife hired an investigator to establish the true professional activity of her ex-husband, who had accumulated debts arising from non-payment of obligations set after the divorce. The person investigated argued that the reports had infringed his privacy and right to his own image.
The Supreme Court dismissed the claim: there was a legitimate interest; the purpose was to obtain evidence for existing proceedings; the operation had been carried out respecting spatial limits; and the information was related to the subject matter of the investigation.
The case explains the investigator's legal position better than any abstract definition: a person had a right and needed to prove relevant facts in order to make it effective.
Moreover, the LEC expressly recognises our report
Article 265.1.5 LEC specifically mentions reports prepared by legally licensed private investigation professionals.
Private Security Act: the investigator can investigate and obtain information and evidence.
Civil Procedure Act: the resulting report can be brought into the proceedings.
Constitution: the parties have the right to use the evidence relevant to their defence.
The three pieces fit together.
Three requirements make the assignment lawful
A licensed investigator
Private investigation legally reserved to investigators must be carried out by licensed professionals, within the framework established by the Private Security Act.
Legitimate interest
We do not investigate out of curiosity. The person requesting the service must demonstrate the legitimate interest justifying the assignment, and it must be documented.
Proportionate investigation
The existence of a legitimate interest does not permit the use of just any method. The law prohibits investigating private life as it unfolds inside homes or reserved places, and requires respect for privacy, honour, one's own image, the secrecy of communications, and data protection.
It also imposes reasonableness, necessity, suitability, and proportionality.
These limits are not a weakness of the profession. They are precisely what turns a private investigation into professional evidence.
What's unlawful isn't hiring an investigator
What can be unlawful is asking them to do what the law prohibits: entering a home, intercepting communications, obtaining passwords, unlawfully accessing private accounts, invading reserved spaces, or investigating without a legitimate interest.
A professional agency is not there to carry out whatever the client asks. It is there to turn a legitimate need for information into a legally defensible investigation.
Conclusion: defending a right often means proving a fact
Yes, hiring a private investigator in Spain is fully legal.
Because a regulated profession exists. Because the Private Security Act allows information and evidence to be obtained and provided on behalf of legitimately entitled third parties. Because the LEC expressly recognises their reports. And because, when that evidence is necessary to support a claim, obtaining it serves an essential fundamental right: the right to defend oneself by proving one's case.
A good investigator does not operate outside fundamental rights. They work among them.
They protect the client's rights while respecting those of the person under investigation, and turn what someone knows, suspects, or needs to prove into something far more useful before a court: a proven fact.
Truth has a method.