On 9 December 1797( Cannot occur after Transportation !), Cadman was sentenced to transportation for life at the Worcester assizes, after being arrested at Bewdley on the charge of stealing a horse. Cadman was transported aboard the Barwell, which left Portsmouth, 7 November 1797 and reached Sydney, 18 May 1798. In 1809, Cadman became the coxswain of a government boat.
Whilst in the service of the Government as a coxswain, he lost an eye.
Cadman received a conditional pardon from Governor Lachlan Macquarie in 1814 and a free pardon in 1821. Cadman became the master of the Cutter "Mars" in 1825, which took 25 prisoners to Newcastle.
He was then promoted to the position of Superintendent of Government Boats at Sydney in 1827 on a salary of £91, until he retired in 1845. When that position of office was abolished in 1845, Governor Sir George Gipps recommended "his great respectability" and arranged for him to be paid a retiring gratuity of £182.
Since 1816 Cadman had occupied a rough stone cottage at The Rocks.
Cadmans Cottage still stands today and is Australia"s oldest surviving house within the city of Sydney. 5,6 January 1818, Cadman received government permission to marry at Sydney. On 26 October 1830 John married Elizabeth Mortimer.
Cadman was buried in the old Devonshire Street Cemetery.