Mr McGuinness’s IRA past again overshadowed his presidential campaign when he was confronted while canvassing in Athlone, Co Westmeath, by David Kelly, the son of the late Private Patrick Kelly.
Pte Kelly and trainee garda Gary Sheehan died in a shoot-out at Derrada Woods, Co Leitrim, in 1983 when trying to rescue businessman Don Tidey, who had been kidnapped by the IRA.
Holding a photograph of his father, David Kelly demanded the Sinn Féin presidential candidate reveal the identity of the killers. “I believe you know the names of the killers of my father and I want you to tell me who they are.
“You were on the army council of the IRA.”
When Mr McGuinness denied being on the army council and insisted he had no knowledge of the killers, Mr Kelly labelled him a liar.
“[My father] was loyal to this Irish Republic and I am loyal to him as a son and I’m going to get justice for him,” he said. “I want your comrades who committed this crime to hand themselves in to the gardaí.”
Mr McGuinness said: “I don’t know who was responsible for the killing of your father, but I fully and absolutely sympathise with you.
“I have been at the heart of a very important peace process in the North over the last 20 years which has brought conflict and violence and death to an end and I am going to continue with that work because that’s the work of peace.
“This is in the past, you are heartbroken on account of it and my sympathy is 100% with you and your family.”
Former army officer John McNamara also offered his sympathy but defended his decision to canvass for the Sinn Féin candidate.
“I am canvassing for Martin McGuinness because he is a peacemaker,” he said.
Mr Kelly told Mr McNamara: “You are spitting on my father’s grave.”
Later, in Trim, Co Meath, Mr McGuinness said: “As a republican leader I have never and would never stand over attacks on the gardaí or the defence forces.
“For many years now I have dedicated myself to building and upholding a peace process which will consign violent conflict to history. That peace process is recognised as one of the most successful in the world. We are now in a far better place.”