Martin John Greer was born on the 2nd May 1893 in Kiltoom, Co. Roscommon. He was the eldest son of Sergeant James Greer, 49202, R.I.C., and his wife Nora (née Nolan), a schoolteacher. James and Nora Greer had ten children.
On the 1st April 1914 he was appointed to the R.I.C. at the age of 20 years, one month short of his 21st birthday. He was recorded as being 6'1⅛", a Catholic, with no previous employment. On completion of training on the 4th October 1914, Constable Martin Greer, 67768, was allocated to Co. Kerry. On the 26th March he was transferred to the R.I.C. Reserve at the R.I.C. Depot, Phoenix Park, where he worked at Dublin Castle as a clerk.
Martin Greer when he died was single, 27 years and 9 months old, with 6 years and 10 months of service. He is buried in the R.I.C. plot at Glasnevin Cemetery, Dublin.