Marshall studied law and was called to the Bar at the Middle Temple in 1868.
He lost his right arm as the result of an accident at the age of 16. After taking a degree at Exeter College, Oxford he became a High Church Anglican minister in 1852 and was appointed curate in Trysull, near Wolverhampton. In 1854, he became curate at Saint Bartholomew"s Church, Moor Lane, in the parish of Saint Giles, Cripplegate, London.
He practised law in Manchester where he helped to found The Catholic Times.
In 1873 he accepted an appointment in the British Colonial Service as Chief Magistrate and Judicial Assessor to the native chiefs in the Gold Coast, arriving there in July. On the breaking out of the Ashanti War in 1874, he secured the chiefs" assent to the impressment of their tribesmen, and was of great use throughout the campaign in raising levies.
He made a good impression on the Ashanti people, who regarded him as a veteran general who had lost his arm in battle. In 1874 Marshall left the Cape Coast and transferred, on his promotion to Puisne Judge, to Lagos, arriving there in January 1875.
He served as Chief Justice of the Gold Coast (now Ghana) from 1880 to 1882.
Marshall believed that the Gold Coast offered a very favourable environment for the return of Roman Catholic missionaries. In 1879 he asked the Office of the Propagation of Faith in Rome to provide missionaries. There is a plaque inside the church in their memory.
lieutenant was unveiled on 11 August 1999, 100 years after his death.
The Knights and Ladies of Marshall, a lay association of Ghanaian Catholics, visit the church in Mortlake annually to celebrate a mass in his memory.