The use of hidden cameras is often associated with the invasion of privacy because a priori indicates that someone is being filmed without having given any kind of consent for such. However, not everything is what it seems.

In reality, whoever records a conversation with another does not commit any conduct contrary to the Spanish constitution, provided that the recorded conversation does not include "facts proper to the sphere protected by the right to privacy enshrined in Article 18.1 of the Spanish Constitution."

However, when we are recording a conversation with third parties without any intervention in the conversation, the case changes shape. Because it is supposedly illegal to record someone's dialogue without either of the parties having knowledge of that fact. Although, there are legal ways to do it. That is when there is an official investigation, recording is allowed. Of course, for that, it is necessary a judicial authorization or then the hiring of a detective that participates in this dialogue.

In the field of visual recordings, a private investigator is authorized to capture images without prior authorization from the person being investigated, provided that he is in the exercise of his functions and during the course of the investigation. This is because there are certain events that are only possible to try with this type of recordings. It should also be emphasized that the use of hidden cameras by these professionals constitutes a judicially accepted means of proof.

But, as is obvious, in spite of that, clients do not always believe in the legality of these investigations, particularly in regard to the data protection law.

That is why we see the need and importance of making it clear that whenever the three basic requirements of the Supreme Court are obeyed (proportionality, necessity, and suitability), the data collected at the request of a party, by private detectives, with hidden cameras are perfectly legal.