Seán MacDiarmada’s court martial was one of the lengthiest of those carried out involving the leaders of the Rising.

In addition to the charge of staging an armed rebellion with the intention of assisting the enemy, MacDiarmada faced an additional charge of causing “disaffection among the civilian population of His Majesty”.

He was found guilty of the former charge, but not guilty of the latter.

His court martial took place on May 9th, 1916, and was presided over by Lieut Col Douglas Sapte assisted by Lieut Col Philip Bent and Maj Francis Woodward.

More time was taken over MacDiarmada’s trial presumably because of pressure on Gen John Maxwell from London to ensure that proper procedure was followed.

The first witness for the prosecution was Det Constable Daniel Hoey of the Dublin Metropolitan Police, who was later assassinated by Michael Collins’s “squad” during the War of Independence.

Hoey said he had observed John McDermott (as he was known to the police) for 3½ years and saw him associate with the leaders of the Irish Volunteers including Thomas Clarke, Patrick Pearse and Joseph Mary Plunkett.

Hoey said the Irish Volunteer newspaper was MacDiarmada’s chief source of income. A copy of the newspaper was produced as evidence.

Second Lieut WH Ruxton of the 3rd Royal Irish Rifles said he encountered MacDiarmada on the last day of the Rising when they were gathering surrendered rebels at the top of Parnell Street.

MacDiarmada, who was struck down by polio in 1911 and lost the use of one leg, told him that he could not walk to custody. Ruxton continued: “One of the others told me his leg was paralysed. I asked the accused, ‘how did you get into this affair?’ The accused replied to the effect that he had his place in the organisation.”

It would appear from MacDiarmada's file that the court martial members wished to establish that the man known to the authorities as John McDermott was actually Seán MacDiarmada.

Edward Gannon, a clerk at Mountjoy Jail, recounted that the accused had spent time there in June 1915 and had signed his name Seán MacDiarmada.

The bottom half of the Proclamation with MacDiarmada’s signature also appears in his court martial file, but there is no account of the sequence of events that led it to it being produced as evidence.

Maxwell was under a lot of political pressure to stay the executions so the production of the Proclamation as evidence may have been significant in his decision to approve the death penalty for MacDiarmada and Connolly.

Also there is a note written by MacDiarmada on Easter Monday which was produced in evidence. It states: “I want all you men to report to me at Liberty Hall by 11am, today Monday with full equipment - Seán MacDiarmada.”

He was the penultimate leader of the rebellion to be executed. He was shot by firing squad on May 12th just before James Connolly’s execution. In his last letter he wrote to his brothers and sisters, “I die that Ireland might live.”