To solve a crime is not an easy matter, when a judge has to assess the proofs gathered during the instruction, may need the assistant of experts who have the knowledge necessary to extract the conclusions which will determine the responsibility and the details of how the crime was committed.
To start we need to take into account the art. 299 of the Spanish Procedural Law (in Spanish Ley de Enjuiciamiento Criminal, henceforth LECrim) if we are in the ordinary procedure or the art. 777 LECrim if we are in the abbreviated procedure, the distinction between both procedures has to be find in the art. 757 LECrim. Either the art. 299 or the art. 777 in essence state the same, the summary is destined to clarify the authorship and the details of the crime. For this, we have the diligences expressed in the law, as the declaration of the suspects and witnesses, the ocular inspection, or the experto report, which is the object of this writing.
At the beginning, I have already hinted the purpose of the diligence of the expert report, but we can be more precise, the art. 456 LECrim stated that the judge would accord order the expert report when to know some important fact or circumstance, would be needed or convenient scientific or artistic knowledges. Here we have the two essential features of this diligence, is a diligence ordered by the judge, and only will be necessary when the judge lacks the depth of knowledge required to analyze the proof obtained during the investigation. To what I have said there is an exception, because the parties has the right to name an expert on their account when the expert analysis is unrepeatable in the trial, but is possibility is limited, since the expert of the parties will only accompany the judge expert.
Before continue, I think is important to develop the second feature. Although the expert report completes the lack of knowledge of the judge, it doesn’t mean that the judge is tied to what the expert report says. The judge or the tribunal, who will have into account the expert report to determine the guilt of the suspect in the sentence, cannot share the opinion of the expert, the judge or the tribunal are only obliged to follow the rules of the logic, of the science, of the common sense, therefore as in the case of the other proofs practices during the trial, the principles which will apply to the assessment of the expert report will be the valuation of the proofs as a whole and their free assessment. The above is in accordance with the article 741 LECrim, which states the valuation of the proofs by the judge according its conscience, and the art. 117.1 of the Spanish Constitution which states the power of the judges to administer justice. Thus the judge or tribunal which will dictate sentence is not obliged to follow what is said in the expert report.
In the last paragraph we have touch another import matter, we have talk about the trial, and even before we have said that the parties have the right to name another expert when the report is unrepeatable during the trial. As we already know, the only proof with the capacity to destroy the presumption of innocence of the accused is the proof practiced during a public trial, as consequence the expert report must be repeated during the trial to be capable to destroy such presumption of innocence. Normally this is done with the declaration of the experts during the trial. This requirement developed by the Spanish jurisprudence is to guarantee the right of defense of the accused, and concretely the principle of contradiction which is part of this right of defense. As in the case of the expert named by the parties when the expert report is unrepeatable during the trial, the parties have also the right to contradict this proof during the summary, this is guaranteed by the art. 476. Notwithstanding the above, are proofs which should be practiced by an expert and which cannot comply with the principle of contradiction during its practice, an example is the taking of ADN vestiges in the place of the crime, because this normally is done in a pro-procesal phase where indeed the suspect of the crime is not yet determined. In this last case, the principle of contradiction should be guaranteed later, in the trial, with the declaration of the police officers which analyzed this sort of proof.
Summing up, the expert report is a diligence ordered by the Instructor judge during the summary, which later will not bind the final resolution of the tribunal who will judge the case, and where the most important is to guarantee the right to defense of the accused or suspect complying with the principle of contradiction.