A suspect may be imprisoned before there is a firm sentence against him. The legal artifact designed to comply with this undertaking is the provisional prison, which is a preventive measure, it means that is aimed to guarantee the effectiveness of the future sentence which put an end to the procedure. The above is valid to both sorts of preventive measures, personals and reals. The former affect directly on the subject object of the measure, and they constrain the capacity of the subject to move with liberty, and the latter, are measures aimed to limit the economical resources of the subject being investigated.
In the case of the provisional prison we are before a personal preventive measure. The Spanish Penal Procedural Law (in Spanish Ley de Enjuiciamiento Criminal, henceforth LECrim) has divided them in three, the detention, the provisional prison, and the provisional liberty, but the three restrict the same fundamental rights recognized in the Spanish Constitution (henceforth, CE). As preventive personal measures that restrict the mobility of the suspect, they are in conflict with the right of liberty (art. 17 CE), the right to choose freely a residence and to circulate through de country (art. 19 CE), and indirectly, though related, the right to the presumption of innocence of an investigated (art. 24.2 CE).
All the preventive measures are accorded following the same legal prescriptions, there are two requisites which should be complied: the appearance of good right, and the risk caused by a belated actuation. The appearance of good right (art. 503.1.1º and art. 503.1.2º LECrim), is a requisite which is compiled when there are sufficient evidences to attribute a crime to a determine suspect, the concept of sufficient evidences varies depending the moment of the procedure, for example the evidences which support a sentence have to have the enough strength to destroy the presumption of innocence of an accused, while in this case the evidences should not be as strong, will be enough with a high probability of the culpability of a suspect, if it is compared with the probability of its innocence. With respect the risk caused by a belated actuation (art. 503.1.3º and art. 503.2 LECrim), we are referring to the adverse consequences which may arise if the preventive measure are not rapidly applied, as the risk of flight of the suspect, or that the suspect would use its liberty to destroy proofs of the crime.
The provisional prison will come after another personal preventive measure, logically first a suspect should be detained to later be put at judicial disposition (art. 505 LECrim). To pass to one measure to the other, there will be an audience where the parties or the public accusation will interest the provisional prison or the provisional liberty with a fine of the suspect.
Since we are before a measure which restricts a fundamental right, this should be adopted through a motivated resolution of the tribunal (art. 506 LECrim). The resolution should have the form of an “auto”, where the Instructor judge should explain the motives which have brought him to this decisión. Basically the auto will discern about the reasons that justify the measure from the point of view of the article 503 LECrim, and also will be a ponderation of the interests confronted, the right of liberty of the suspect (art. 17 CE) and the achievement of the legitimate constitutional end which the measure is aimed to comply.
Finally, the provisional prison has not the effect of a judged thing, it means that according to the art. 539 LECrim, the resolution where is accorded the provisional prison will be reformable during all the cause. Is possible that the personal circumstances of the suspect which at the beginning of the cause made the Instructor judge to decide the imprisonment, have changed. Or that the results of the investigations carried out don’t provide the evidences which incriminate the suspect. In both cases, the Instructor judge must release the investigated and put him in liberty. Notwithstanding the above, we have to bear in mind that at the onset, will be enough to adopt this provisional measure, according the objective circumstance of the gravity of the crime investigated.