The art. 17.1 of the Spanish Constitution provides that no one can be deprived of their freedom except in the “form provided by law”.

The law tells us, more specifically art. 503 of the Criminal Procedure Law, that provisional detention may only be decreed when the following REQUIREMENTS are met:

1.- Regarding the crime: the existence of facts that present the characteristics of a crime punishable with a maximum penalty of two years in prison or less, or less if the person investigated has a criminal record for intentional crime.

2.- Regarding the person investigated: sufficient reasons to charge the person investigated with the commission of said crime.

3.- Regarding the purpose: that through provisional detention one of the following purposes is pursued:

a) Ensure the presence of the person investigated in the process when a flight risk can be rationally inferred . In order to assess the existence of this danger, the nature of the act, the seriousness of the penalty, the family, work and economic situation of the latter, as well as the imminence of the holding of the oral trial, will be considered jointly. In any case, provisional detention will be agreed upon when at least two requisitions have been issued for his appeal and search by any judicial body in the previous two years (in these cases the minimum limit of the crime penalty will not be applicable).

b) Avoid concealment, alteration or destruction of relevant evidence sources for prosecution in cases where there is a well-founded and specific danger. In order to assess the existence of this danger, the ability of the person under investigation to access the sources of evidence or to influence other persons under investigation, witnesses or experts or who could be, will be taken into account.

c) Prevent the person being investigated from acting against the victim , especially when the victim is a partner (or ex-partner), relatives or minors who live with the victim (in these cases the minimum penalty limit for the crime will not apply).

d) Avoid the risk that the investigated commit other criminal acts . To assess the existence of this risk, the circumstances of the event will be taken into account, as well as the seriousness of the crimes that could be committed.

Punitive or anticipation of punishment is ruled out as constitutionally admissible purposes. The primary purpose of provisional detention is linked to the need to guarantee the normal development of the criminal process in which the measure is adopted, especially to ensure the presence of the accused at trial and to avoid possible obstructions to its normal development.

Taking into account the foregoing, our doctrine has determined that there is a reinforced duty on the part of the judicial body to motivate the resolution that agrees to provisional detention, since only an adequate motivation makes the factual circumstances that were taken into account knowable and monitorable, to the effects of being able to revoke or modify this provisional measure later.

Provisional detention will last for the essential time to achieve any of these purposes and only while these reasons subsist, with a maximum period that varies depending on the maximum severity of the sentence for the crime under investigation: one year if the crime has a custodial sentence. equal to or less than three years or two years if the custodial sentence indicated for the offense is greater than three years, and exceptional extensions of six months or two years, respectively, may be agreed.

In cases of conviction, and for the duration of the appeal, provisional detention may be extended up to the limit of half the sentence effectively imposed in the appealed sentence.

When provisional detention has been agreed to avoid the concealment, alteration or destruction of evidence, its duration may not exceed six months.

Our Constitutional Court has established doctrine saying that provisional detention must be applied under the parameters of the principle of exceptionality , linked to the fact that in criminal proceedings the principles of favor libertatis or in dubio pro libertatis govern . For this reason, the interpretation and application of the norms regulating the provisional detention measure “must be done with a restrictive nature and in favor of the fundamental right that such norms restrict, which must lead to the choice and application, in case of doubt, of the least restrictive rule of liberty.

Under the umbrella of the principle of exceptionality, pretrial detention is prevented from being applied in cases in which the pursued purpose can be achieved through less burdensome alternative measures. Said principle obliges the Judge to find out if the legitimate purpose that he pursues can be achieved through an alternative measure.