 O'Doherty was born in Dublin on 7 September 1823, although other sources including the Dictionary of Australasian Biography indicate he was born in June 1824.Charles Gavan Duffy, in his "My Life in Two Hemispheres", states that O'Doherty was still under age when he was arrested in July 1848; however, Gavan Duffy was writing 50 years later.O'Doherty received a good education and studied medicine, but before he was qualified, joined the Young Ireland party and in June 1848, together with Thomas Antisell and Richard D'Alton Williams, established "The Irish Tribune".