By whom, how, why? The expertise of cultural property makes the object of an abundant jurisprudence. Of the discovery in the authentification. Profession to become there, the expertise is more and more frequently the fruit of a teamwork today bringing in, under the direction(management) and the control of the expert, the “knowledgeable individuals” and the scientific analysts, at least for the valuable rooms(parts,plays). Recognized specialists of a period of the art history, all or part of the work of an artist, even a technique, the knowledgeable individuals bring to the expert, besides the moral pledge ensuing from their fame, a very precise knowledge in fields of analysis which is theirs. The scientific analysts, for their part, supply data susceptible to facilitate the identification of the author of a work, to allow its dating, to characterize the employment(use) of a technique, to emphasize stages of the process of creation…. By the coordination of these activities and the combination(overall) of these data, the relevance of which he(it) appreciates(estimates), the expert gathers(combines) a body of evidence which allows him(her) to pronounce on the identification and, correlatively, if need be, on the evaluation of the work subjected(submitted) to its appreciation. The fulfillment of the work of the expert thus supposes today, among others skills, that this one possesses a detailed knowledge of the limits of the various existing scientific methods of analysis. Held(liked) a simple best effort undertaking and an accountant of the deniers of his customer, it is up to him(her), indeed, not to resort(turn) systematically to the employment(use) of all the methods of scientific analysis, but to decide on the opportunity of the use of these. He will then have to discuss the relevance of the results(profits) so obtained. Whatever some ardent supporters were able to say it, the scientific analysis does not indeed establish(constitute) a panacea making useless the appeal(recourse) to the expertise. She is simply an assistant of this one, in the same way as the appeal(recourse) to the knowledgeable individuals. It is not of what had thought the judges in 1951, by making the decision, about the auction of a panel(sign) representing a Virgin(Virgo) to ears, to grant(tune) damages on the foundation of faults committed by the experts having drafted the catalog of the sale. For the trial judges, these faults consisted in the absence of use of the scientific said methods, in the realization of a simple superficial examination of the room (part,play) and in the excessive confidence(trust) in the authenticity of this one because of the origin. This debatable decision made press on the experts an obligation (bond), unrealistic, to resort(turn) systematically to the scientific analyses. She(it) was reformed by the judges of the Court of Appeal of Paris who, on February 12th, 1954, while admitting the responsibility of the experts, took care of raising(finding) that, if these ” had been lacking caution in the writing(editorial staff) of the catalog “, they were not kept for all that ” to subject(submit) to scientific examinations all the put on sale paintings(boards) ” .C’ is in the same sense(direction) as pronounced recently the judges of the Court of Cassation, in the said affair(business) of the ” Chick of the brothers Pardo “. On September 17th, 2003, they decided that judge them the Court of Appeal of Paris – by raising(finding) in particular that ” a cleaning or scientific or radiographic measures or other investigations still ” would not have been enough to establish the authenticity of the litigious painting(cloth) with regard to(compared with) a copy of time(period) – had correctly motivated their decision to reject the action(share) in responsibility instituted against auctioneers’ company(society) in charge of the sale. The difficulty consisting in the case in point in the fact of distinguishing the original of the former excellent copy, the observation was we cannot anymore relevant, even if the mission of searches and investigations confided to the house of sales aimed, in conformance with the ways to use, at the appeal to “every expert, knowing, or proceeded scientific”. The relations between the scientific analysis and thus the expertise perfectly clear and coherent, in the eyes of the jurisprudence, – what can only be a security of safety for all the professionals. The scientific analyst, in the same way as knowing him, is an auxiliary of expert, often precious, but not always essential. The expert has indeed by no means to resort in any measure of scientific analysis when this one does not present interest with regard to the mission which is confided to him