In the aftermath of a reform in Quebec’s Family Law in 1980, the author demonstrates the increasing relevance of blood samples and biological tools in Civil Law. They are especially useful in matters of filiation whether it be concerning its establishment or its contestation. In fact, while the provisions of the Civil Code of Lower Canada neglected to consider biological elements, this article analyzes the evolution of the law and its eventual submission to the science and indisputable truths provided by genetics. As such, the author goes beyond a legislative, jurisprudential and doctrinal analysis of the state of the law by evaluating its normative functions with respect to factual realities.