The importance of scientific knowledge in criminal trials

High technical skills are now an essential requirement in a multitude of cases concerning criminal proceedings, such as events related to crimes to protect health and safety in the workplace, environmental crimes or even corporate and bankruptcy crimes. In this context, “scientific knowledge” is utterly crucial for all the figures involved, from lawyers to prosecutors, to judges.

Having to deal with issues that are very technical and far from legal competence per se puts criminal law operators in the condition of expanding their culture and training. They also have to rely on additional specialists for specific subjects, appointing them as experts or partisan consultants during trials.

And it is precisely the confrontation between legal professionals and “technical” experts – through the hearings of the latter and the acquisition of their reports – that has generated a complex debate on the role of scientific evidence in law.

What does scientific proof in the judicial field mean?

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Jurisprudence includes in the category of scientific proof all the evidence that, starting from a proven fact, must use a scientific law to ascertain or confirm a further fact yet to be proven.

In fact, the criminal trial Judge does not have specific technical-scientific knowledge and must therefore base their assessment on the opinion and competence of the experts or partisan technical consultants. In this sense, the Judge is not an advocate of a scientific law but a user. Starting from the famous Cozzini ruling, this principle is now consolidated.

The concept has been confirmed by the reasons recently given by the Court of Cassation concerning the well-known story of the Viareggio massacre.

“On the level of principles, it should be remembered that the teaching of the jurisprudence of legitimacy has now become common heritage, at least for the operators of law, according to which the Judge is precluded from becoming the maker of the scientific law necessary for assessment in the judgments due to expert knowledge. Since the Judge is the bearer of a “legitimate ignorance” concerning scientific knowledge, it is a matter of evaluating the scientific authority of the expert who transfers their knowledge of science into the trial; but also understanding, especially in the most problematic cases, if the proposed statements find common acceptance in the scientific community.”

“From this point of view, the Judge is effectively and in the highest sense peritus peritorum: the guardian and guarantor of the scientificity of the factual knowledge expressed by the trial”, highlighting that “the evidence that the parties are required to provide cannot be other than what the Judge needs. (…) If the Judge needs to know which is the most accredited scientific thesis in the community of scholars, the party who intends to appeal to that thesis has the burden of proving such accreditation while the other party can and must resist (also) on that ground.”

It is undoubtedly a difficult task, both for the Judge called to deliberate on a specific matter and for the parties who, through the appropriate skills, have to demonstrate the greater authority of the scientific thesis supported by their experts.

During the same sentence, the Supreme Court also recalled that:

“The sentence can only be pronounced when the accused is guilty beyond a reasonable doubt. This implies that the statement of responsibility presupposes – limited to the point under consideration – that it is acquired beyond any reasonable doubt that the cover law on which the accusatory approach is built is seen as the most accredited by the scientific community. (…)”

“It is therefore necessary to demonstrate only the marginality – not on a logical level but a comparative level – of the other theses in circulation. On the other hand, for the defense it is sufficient to demonstrate the existence of serious doubt regarding the greater fortune of the theory wielded by the prosecution (…) So that the doubt that may be sufficient to make the accusation fail belongs to the rank of scientific explanation that one would like to be used by the Judge.”

In conclusion, what we illustrated so far highlights the increasingly central role played by the professionals involved in criminal trials that have very complex scientific matters as their subject.