The aim of this article is to do a comparative analysis relative to the investigation of biological paternity of children born out of wedlock in Brazil and european countries, based on the research of legislative documents through the internet and the consultation of legal bibliography in the area of family law. The legislative typology was made - absolute biological truth and relative biological truth according to the following variables: forms of paternal attribution (voluntary/court ordered), type of demanded consent for the performance of the genetic test (voluntary/forced), author of the investigation (state/other) and the time limit of the investigation (existence of process deadlines/no process deadlines). The absolute biological truth occurs when the investigation of paternity is compulsory and the court might order and force the submission to a genetic test. The dominating trend is relative biological truth. In all analysed countries it has been verified that the resource to genetic testing is preponderant when establishing affiliation relations. Even in countries where it's not possible to force an individual to the submission of a genetic exam, there are more subtle ways of submission, that include the application of fines or the assumption of paternity based on a refusal to perform the genetic exam.
Paternity; biological truth; genetic test; informed consent