he was born in the town of risør as a son of jacob wetlesen prebensen (1808–1892) and wencke kristiane grove. he finished his secondary education in 1868 and took the cand.jur. degree in 1873. he was hired as a clerk in the ministry of church affairs in 1876, and from 1878 to 1881 he was a deputy judge in romsdal district court. he was also acting district stipendiary magistrate for some time in the absence of district stipendiary magistrate roll. from 1881 to 1887 he was a clerk in the ministry of justice and the police, before being hired as chief of police in vardø in 1887.