John Thomas Spratling was born in May of 1840. Before joining Scotland Yard in late 1870 he worked as a clerk. In his early years he was transferred often between divisions. In 1873 he was promoted to Sergeant, then in 1882 to Inspector third class. In 1887 he was promoted to Divisional Inspector of J Division, which encompasses Bethnal Green. In 1888 he, along with Joseph Helson, investigated the murder of Mary Ann Nichols, which had occurred in their division. He wrote the initial report on the murder, but the case was eventually removed from Spratling's jurisdiction, and he had no further involvement in the case. At the time he was mostly ignored by the press, and remains one of the less well-known inspectors involved in the case. In 1894 he was transferred to Purfleet. He retired in March of 1897, at the age of 57.
He had a wife named Emma, with whom he had two children, one of whom survived to adulthood. He died c. 1934 at the age of about 94.