The valorization of scientific evidence provided by the expert as evidence in the trial framework has been revised, as well as the role of the judge, in light of the assumptions derived from the Daubert Judgment. The criterion of “general acceptance” of evidence obtained from the published literature in journals subjected to peer-review and the expert’s reputation can be helpful, particularly in cases where there is an open debate within the scientific community. It is the judge, however, who must take on the role of gatekeeper of the validity of evidence, to consent to its probatory admissibility, through a preliminary comprehension of the methods of science. The evaluation of reliability and admissibility of evidence is also reflected in the areas of medical malpractice and professional liability. Standards of care may be derived from an analysis not only of the guidelines, but also of other scientific sources to be subjected to the usual proof of admissibility, as well as new research paths that take account of personalized medicine and the application of guidelines to the individual.