J.G. de Labat van Alphen, magistrate, author and collector of prehistoric remains, passed the matriculation examination of the University of the Cape of Good Hope in 1892. After serving as an assistant teacher in government schools for two years he entered the civil service of the Cape Colony in January 1895 as a clerk in the magistrate's office of the Wodehouse district at Dordrecht, Eastern Cape. During the next few years he worked at several other places in the Cape Colony, from 1898 also as acting Dutch interpreter and translator at the Eastern Districts Court in Grahamstown. In 1902 he was appointed assistant magistrate at Jansenville and after serving in several other towns became chief clerk in the Attorney-General's office, Cape Town, in August 1908. During these years he had continued studying in private, passing the examinations of the University of the Cape of Good Hope (an examining body only) and was awarded the BA degree in Literature and Philosophy in 1907. He subsequently worked as assistant magistrate and later magistrate in Hopefield (to 1913), Cape Town, Tarkastad (from 1915) and other places, including Barkley West (1929) and Worcester (1930), until his retirement in 1935.
Van Alphen had a life-long interest in South African prehistory. He was involved in several significant discoveries, including that of the Canteen Koppie skull at Barkley West, which he presented to the McGregor Museum in Kimberley. Among others he collected stone artefacts at Pniel River, Barkley West and Windsorton. His finds went to the South African Museum, Cape Town, the Archaeological Survey, Johannesburg, and the British Museum (Natural History). In 1929 he wrote an article on 'Stone implements in South Africa' which was published in Die Huisgenoot in two parts (13 December 1929 and 28 March 1930).
Van Alphen was the author of a novel, Jan Venter, SAP, a plain narrative of everyday life at a South African police out-station (Cape Town, 1929). He was survived by his wife, a son and a daughter.