He was born on 24 May 1906 in the family of a Lublin confectioner. After graduating from high school in his hometown, he took up legal and economic studies at the newly created Catholic University of Lublin, receiving a master’s degree in law at the Jan Kazimierz University in Lviv in 1928. He then went on to study at the Sorbonne in Paris, where, among others, he listened to lectures by Louis Le Fur (1870–1943). Martyniak obtained his doctorate at the Institut Catholique in 1931 on the basis of a thesis entitled Obiektywna podstawa prawa, written originally in French (Polish translation: 1949). In 1931, he returned to Lublin and was employed as an assistant at the Theory and Philosophy of Law Section at the Faculty of Law and Economic Sciences of the Catholic University of Lublin. After obtaining his doctorate in law in Lviv two years later, he became deputy professor of theory and philosophy of law. In 1939, a few months before the outbreak of the war, he received his advanced research degree (habilitation) from the Jagiellonian University with prof. J. Lande, based on a work criticising the normativist doctrine developed by H. Kelsen. In October 1939, when the Catholic University of Lublin commenced lectures without agreeing this move with the German authorities, Martyniak was arrested, along with thirteen other professors. Imprisoned for several weeks at the Lublin Castle, he was shot by firing squad on 23 December 1939 at the Jewish cemetery in Kalinowszczyzna.