John Martin was tried at Justice Hall in the Old Bailey, London on the 3rd of July 1782 for stealing clothing with a value of 39 shillings. He was sentenced to transportation for seven years and left England on the Alexander aged about 29 at the time (May 1787). He had no occupation recorded.

  Described as "a black", and "A sober industrious man". At the time of landing at Port Jackson he had technically only one year to serve.  On August 30 1788 he received 25 lashes for lighting a fire in his hut. In July 1789 he was a witness at the trial of John Callaghan.
On November 29 1792 he received a grant of 50 acres at the Northern Boundary Farms, having married at Ann Joy (Neptune 1790) on 26 August , and was off stores by 24 October 1795. In March 1798 he was noted as the only one of the old settlers remaining at The Ponds, "a sober and industrious man, yet very poor". By mid 1800 he had sown 3 acres in wheat with six acres ready for planting maize. He owned one hog and was off store, but his wife was still publicly rationed. They had no children.
In 1802 Martin still held his 50 acres, 26 of them clear, nearly nine in wheat and six ready for maize. He and his wife were in grain, one as garden, 20 for pasture and two fallow: he owned two sheep and 12 hogs, six bushel of maize: he was victualled (as a constable) but his wife was not, nor were the one convict and one free man he employed. No children were indicated. Through the years he remained a constable, and also pound keeper in 1820.
Martins wife Ann died at Parramatta on 12 February 1806. He then married a Mary Randall on 20 July 1812: she was probably the daughter of John Randall (another black) born on 4 December 1793, with whom he may have been living shortly after his wife's death. Their children were John (1807), Sophia (1809), Francis (1810), Henry (1813) and Hannah (1815).
In 1828, age given as 72, he was pensioned as a constable and still held 50 acres in the Northern Boundary district, with 40 cleared (15 of them cultivated). He owned 3 horse and 20 sheep and employed a convict laborer.
In his will dated 17 December 1837 (signed with mark) he discriped himself as a settler, Pennant Hills Road, Field of Mars. He left his wife one shilling and directed that his farm be divided among his 5 children. Isaac Mobbs and Richard Partridge were executors and the estate was valued at und 25 pounds (excluding realty), probate not being granted until 19 October 1841. He died at Field of Mars on 21 December 1837, age given as 88, and was buried at St Johns Parramatta.
He was a Protestant.
The clothing he stole was 2 coats,waist coat and a pair of stuff breeches it was the property of Stephen Turnbull. He also stole 2 stuff coats, 2 cloth waist coats, 2 pairs of cloth breeches, a cotton waist coat, linen waist coat, 1 petticoat, cotton gown all the property of John Turnbull stolen from his home on 8/5/1782