Although the search for objective truth as the end of the process is not unanimously accepted in the theory of evidence, many authors agree that the means of proof are aimed at clarifying the facts behind the process. Considered in procedural theory as a mechanism to guarantee a fair and impartial process, expert evidence is expected to preserve, through science, the objective truth of the facts and the best understanding of the case by the adjudicators.This study will question whether, in fact, this happens in the practice of expert evidence and what challenges expert evidence poses to achieve these aspirations of neutrality. In particular, the article will show how, given the characteristics of the process today, expert evidence is subject to external and subjective factors that must be considered, demystifying some common beliefs about its impartiality. This would allow for a better understanding and a critical opinion of expert evidence and its influence on decision-making.