In 1846, he enlisted in the Mexican–American War as a surgeon and cavalry captain, apparently using forged medical diplomas from Dartmouth College, New Hampshire, and the Saint Louis University School of Medicine, Missouri.
In 1847, he killed a fellow officer in a duel and fled to England, where he spent some months in a lunatic asylum.
He practised as a doctor in Angaston in the Barossa Valley and was naturalised and admitted to a roll of medical practitioners in October 1850.
[1][2] Dean travelled to Melbourne and Sydney where he wrote for Henry Parkes' The Empire and in 1858 became as a storekeeper at Tinonee, near Taree on the Manning River.
In July 1870, he won the resulting by-election but was again disqualified, this time due to his lack of citizenship.