The new reformation made in the Costa Rican Juvenile Law recognizes the legal personality of the minor, it makes him justice and gives him more responsability for his actions .For all these it has been design a Juvenile Law System with pedagogic, educative and formative ends for the minor transgressor , therefore it can be the object of medico-legal expertize, physical aspects like his body, his tests and psicoanalisis. The porpouse of physical expertize is to establish the age of the minor specially in a high undocumented migration country like ours, where differences of only a months can produce the aplication or not of the law. All the expertizes must respect the dignity, avoid the victimazation once again and be done by forensic experts by their own will. It is also important in medico-legal expertize the constation of capacity of guiltiness, the degree of development and responsability to direct their actions , and ilustrate to the judge and the parties, about the eventuals sanctions to impone.

transgressor; childhood; expertize; coronary; guiltiness; sanctions; manipulation; credibility; prohibition; exploration