Private detectives are regulated by Law 5/2014, of April 4, on Private Security

Article 5. Private security activities

2. Detective offices may provide, on an exclusive and exclusive basis, “Private investigation in relation to people, events or crimes that can only be prosecuted at the request of a party.”

Article 19

Private detectives, at the request of natural or legal persons, will be in charge of: Obtaining and providing information and evidence on private conduct or events that affect the economic, labor, commercial, financial and personal, family or social life in general. except those that affect homes or reserved places. Of the investigation of crimes prosecutable only at the request of a party commissioned by those authorized in the criminal process. Surveillance at fairs, hotels, exhibitions or similar areas.

Article 37. Private detectives

1. Private detectives will be responsible for the personal execution of the private investigation services referred to in article 48, by carrying out investigations in relation to people, facts and private conduct.
4. Private detectives may not investigate crimes prosecutable ex officio, and must immediately report to the competent authority any fact of this nature that comes to their knowledge, and making available all the information and instruments that they may have obtained up to that point.

Article 48. Private investigation services

1. The private investigation services, carried out by private detectives, will consist of carrying out the investigations that are necessary to obtain and provide, on behalf of legitimate third parties, information and evidence on conduct or private events related to the following aspects:

a) Those related to the economic, labor, commercial, financial sphere and, in general, to personal, family or social life, except for that which takes place in homes or reserved places.

b) Obtaining information aimed at guaranteeing the normal development of activities that take place in fairs, hotels, exhibitions, shows, contests, conventions, large commercial areas, public venues with large attendance or similar areas.

c) Carrying out investigations and obtaining information and evidence related to crimes that can only be prosecuted at the request of a party on behalf of the subjects legitimated in the criminal process.

2. The acceptance of the order of these services by the private detective offices will require, in any case, the accreditation, by the applicant thereof, of the alleged legitimate interest, which will be recorded in the contracting and investigation file that opens.

3. In no case may the intimate life of people that takes place in their homes or other reserved places be investigated, nor may personal, material or technical means be used in this type of services in such a way that they violate the right to honor, to personal or family privacy or one's own image or the secrecy of communications or data protection.

4. In the provision of investigative services, private detectives may not use or make use of means, vehicles or insignia that could be confused with those of the Security Forces and Bodies.

5. In any case, the detective offices and private detectives in charge of the investigations will ensure the rights of their clients with respect to those of the subjects investigated.

6. Private investigation services will be carried out with respect to the principles of reasonableness, necessity, suitability and proportionality.

Article 49. Investigation reports

5. Private investigations will be confidential and the data obtained through them may only be made available to the client or, where appropriate, to the judicial and police bodies, in the latter case only for a police investigation or for a sanctioning procedure, in accordance with the provisions of article 25.

Article 50. Duty of professional reserve

1. Private detectives are obliged to keep confidential the investigations they carry out, and may not provide data or information about them except to the people who entrusted them and to the judicial and police bodies competent to carry out their functions.

2. Only through a court order or police request related to the exercise of their functions in the course of a criminal investigation or a sanctioning procedure will it be possible to access the content of the investigations carried out by private detectives.

JURISPRUDENCE

Law 1/2000 of Civil Procedure

In the Civil Procedure Law, in its article 265, Law 1/2000, of January 7, it establishes that the reports made by private detectives have the character of qualified testimony and cannot be challenged by the other party if they are ratified in court.

The Supreme Court defines private detectives as privileged witnesses.

Sentence 17467/1990

“The testimony issued by private detectives has, in favor of its veracity, not only the guarantee of professionalism required and, in principle, presumed in a legally regulated profession, but also that which, undeniably, provides the precise and continued dedication for the purpose of the subsequent testimony to be issued and the complementary accreditations, graphic or sound, with which the latter is usually accompanied.