Söderman graduated from the chemical college in Malmö in 1920, studied chemistry in Altenburg in Germany, and graduated as forestry engineer in 1924. In the mid-1920s he made a long journey on bicycle, first from Sweden to Istanbul, and further to India, Burma and China. He had signed a contract with a police magazine, to which he delivered travelling letters, and during the journey he made detailed studies on how the local police solved their tasks. From 1926 he studied forensic science with Edmond Locard, and graduated from the University of Lyon in 1928 with a doctoral thesis on the identification of gun bullets. In 1930 he was appointed lecturer in forensic sciences at the Stockholms Högskola. From 1934 he contributed with the organization of the police laboratories in New York City. Among the notable investigations he was involved in during this period were the 1931 Ådalen shootings, the 1932 Lindbergh kidnapping, the 1933 German Reichstag fire, and the 1939 murder of Gerd Johansson. In 1939 he was appointed the first head of the National Laboratory of Forensic Science in Sweden, and held this position until 1953.