As provided for in article 335.1 of the Civil Procedural Act (Ley de Enjuiciamiento Civil, LEC), expert opinions are scientific, artistic, technical or practical evidence issued by experts (one or more experts may be involved) in order to assess relevant facts or circumstances in the litigation or to obtain certainty about those facts. Therefore, it is a useful and necessary tool for the resolution of certain claims that require knowledge of other matters that the judges and legal assistants lack, such as, for example, knowledge of medicine, biology, chemistry, architecture, engineering, economics, accounting, etc. Thus, it provides all the scientific-technical (non-legal) knowledge necessary to resolve the controversy that has arisen. Such knowledge is sometimes even needed to assess other means of evidence.

As stated in article 335.2 of the LEC, expert reports must comply with certain requirements, whether they are reports prepared by experts appointed by the parties or reports prepared by experts appointed by the Court: a) they must be issued under oath or promise to tell the truth; b) they must be objective, taking into consideration what may favour and what is likely to cause harm to any of the parties. Experts have a duty to act in accordance with the “lex artis” corresponding to their field of knowledge.

The impartiality and truthfulness of the statements given by the expert is presumed, without prejudice to the possibility that they may be called into question by the parties to the judicial proceedings by the appropriate procedural means. The open and free challenge of the appraisal activity of the expertise is not allowed (Judgment of May 11, 2012 of Section 10 of the Provincial Court of Madrid -JUR 2012/227391).

The latter has recently been confirmed by two Orders issued in proceedings in which an application for damages was being made by parties who had suffered preliminary injunctions for infringement of patent rights and which were subsequently lifted: Order of 29 December 2017 of Section 15 of the Provincial Court of Barcelona and Order of 16 April 2018 of the Commercial Court No. 7 of Barcelona. Thus, the aforementioned Order of 16 April 2018 states the following:

“10. Product withdrawal costs. First of all, it should be pointed out that, as this Court has ruled in the twin resolutions to the present one and as confirmed by the Provincial Court in its order of 29 December 2017, it is not necessary to provide with the expert’s report all the documentary elements that have served as a basis for the expert’s conclusions. The procedural counterpart has at its disposal all the procedural tools, fundamentally the arts. 265.2 and 328 et seq. of the LEC, to request from the plaintiffs all the specific documents that support the conclusions of the plaintiff’s expert to prepare his own expert evidence or to refute those of the other expert.”

The previous resolution also establishes that when there is no challenge of the expert and he has been questioned by the parties under oath or promise to tell the truth, it must be understood per se that the expert’s report complies with the requirements established in article 335.2 of the LEC, specifically that the report issued is objective and truthful. It should be understood that the Courts do not accept the mere generalized criticism of an expert opinion made by the parties for the sole purpose of objecting to the conclusions of an expert opinion, when the latter may use instruments to refute such conclusions or even present different ones:

“11. Therefore, it is considered that the expert’s report provided by the plaintiff has been issued under the conditions referred to in art. 335.2 of the LEC, that there is no reason to challenge the expert and that the expert has been submitted to questions and clarifications by both parties under oath or promise to tell the truth in such a way that, a priori, it is not appropriate to question his conclusions in a generalized manner and, in particular, it must be based on truthfulness, (since the contrary would be punished even criminally), (…)”.

The parties, before an expert report, should be aware that they must use the procedural mechanisms available to them to contradict, when they deem it appropriate, the data and information that the expert has gathered in his report of the corresponding analysis that he has carried out, not being able to limit to an open and free challenge of his appreciative activity.