Patent disputes have a highly technical-scientific component; in a few countries, public officials or judges who know of these disputes have professional training in chemical, mechanical, electrical and other sciences, in addition to law. Hence, in order to apply the law to the specific case that is subject to its decision, officials and judges need to be provided with specialized knowledge, through a suitable test but in a form and language understandable to those who are not trained in the technique. What type of proof is suitable to evidence the infringement of a patent (depending on the subject matter)? What does the judge expect from this type of test? What diligence should the lawyer have to measure the opinion of the expert and his contribution of technical knowledge and the line of the discussion on legal matters? In practice, what problems are confronted to conform the test of experts by the form and design of the procedure of said test? What can be more effective, the expert opinion as pre-constituted documentary evidence or the face-to-face declaration? This multidisciplinary panel will be integrated by a practicing lawyer, experts in areas of technology and by a Judge; this contest of specialties will expose us to the variety of aspects that should be considered in the expert evidence in patent disputes and will present us with experiences and norms of comparative law.