On the morning of 9 September 1942, Garda Detective Sergeant Denis O'Brien was leaving his home in Ballyboden, Dublin. He was between his front gate and his car when he was cut down with Thompson submachine guns. D.S. O'Brien, an Anti-Treaty veteran of the Irish Civil War, had enlisted in the Garda Síochána in 1933. He was one of the most effective Detectives of the Special Branch Division, which had its headquarters at Dublin Castle. According to historian Tim Pat Coogan, "The shooting greatly increased public feeling against the I.R.A., particularly as the murder was carried out in full view of his wife. As she held her dying husband, she watched his assailants cycling past."
Arrest
Following the arrest of Hugh McAteer in October 1942, Kerins was named Chief of Staff of the IRA. Despite a massive manhunt by Gardaí, Kerins remained at large for two years. Travel author Dervla Murphy recounts in her book on Northern Ireland, A Place Apart that Kerins stayed at her family's County Waterford home for two weeks while he was on the run, having given his name as Pat Carney. He had been sent to the Murphy's by Dervla's aunt, Dr. Kathleen Farrell, who was a staunch IRA supporter, and Dervla and Kerins struck up a friendship. Several months after Kerins left the Murphy's, he was captured. Kerins had previously left papers and guns hidden at Kathleen Farrell's house in the Dublin suburb of Rathmines. He telephoned the house, as he intended to retrieve them. However, Dr. Farrell's telephone had been tapped by the Gardaí. On 15 June 1944, Kerins was arrested in an early morning raid. He was sleeping when the Gardaí entered his bedroom and did not have an opportunity to reach the Thompson submachine gun which was hidden under his bed.
Trial
At a trial before the Special Criminal Court in Collins Barracks, Dublin, Kerins was formally charged on 2 October 1944 for the "shooting at Rathfarnham of Detective Dinny O’Brien". According to Coogan, "At the end of his trial, the president of the Military Court delayed sentence until later in the day to allow Kerins, if he wished, to make an application whereby he might have avoided the capital sentence. When the court resumed, Kerins said: 'You could have adjourned it for six years as far as I am concerned, as my attitude towards this Court will always be the same.' He thus deprived himself of the right to give evidence, to face cross examination, or to call witnesses."
Execution
Despite legal moves initiated by Seán MacBride, public protests, and parliamentary intervention by TDs from Clann na Talmhan, Labour, and Independent Oliver J. Flanagan in Leinster House, the Fianna Fáil government of Éamon de Valera refused to issue a reprieve. On 1 December 1944 in Mountjoy Prison, Kerins was hanged by British chief executionerAlbert Pierrepoint, who was employed by the Irish Government for such occasions. Kerins was the last IRA member to be executed in the Republic of Ireland. He was buried in the prison yard. In September 1948, his remains were exhumed and released to his family. He is buried in the Republican Plot at Rath Cemetery, Tralee, County Kerry.