T he documentary Murder in Belfast: Sisters Seeking Justice, about the McCartney siblings’ fight to bring their brother’s killers to justice, makes you wonder. As it outlines the five women’s ceaseless, fearless actions over the last 20 years, you can’t help but ask: when did the IRA and Sinn Féin realise they had picked on the wrong family to cross?

Robert McCartney, a Catholic father of two, was 33 when he was killed in 2005. He was trying to extricate his friend Brendan Devine from a brawl involving members of the local Provisional IRA at Magennis’s bar in the nationalist Short Strand area of Belfast, where the McCartney family had lived for five generations. Devine was seriously injured. Robert was stabbed, brutally beaten and had an eye gouged out. “I’m not going to make it,” he told Devine as they tried to escape the alleyway in which they had been attacked. “Our Gerard needs me.…