In this paper we will develop the "regulation, admissibility and assessment of expert evidence in criminal proceedings", this evidence as part of the means of evidence, is used in the process to demonstrate the veracity of an element of evidence that the procedural parties presume its veracity, this evidence like the others is autonomous with the difference that this means of evidence is prepared by experts, For the judge it is an auxiliary means, which complements his knowledge and which also allows him to better evaluate a piece of evidence, clarifying the doubt about the existence or not of a disputed fact in the process.