He served as an Associate Justice in the Supreme Court of Norway from 1867 to 1905, an unusually long period, and also spent a few years in politics.
He was born in Moss as the son of customs surveyor Nils Lynge Hansteen (1782–1861) and his wife Petronelle Severine Clementin (1787–1829).
[1] In 1886, when Iver Steen Thomle stepped down as Chief Justice of the Supreme Court of Norway, Hansteen had expressed a strong interest in the position.
However, the Liberal cabinet led by Johan Sverdrup chose not to appoint him, probably due to Hansteen's political color.
Later, when the Liberals had lost their majority, Hansteen was asked by King Oscar II of Sweden and Norway to become Prime Minister and form a cabinet of his own in 1892;[1] contrary to popular belief, parliamentarism was not fully implemented in Norway yet.