In this third episode of Inside the Crime, we're brought into the interrogation room where Brian Hennessy was quizzed by Gardaí about the murders.
Sharon Whelan and her daughters Zarah (7) and Nadia (2) had been killed three weeks earlier on Christmas morning 2008.
Former detective Brian Murphy and former Detective Sergeant Jim Lyng take us through their approach to eliciting the truth from Brian Hennessy, knowing they had the vital DNA evidence to place the sub-postman in the rented farmhouse that night.
Within the year, Brian Hennessy was due in the High Court for a trial, a process that would ultimately add further devastation to the family.
Then, he would stun the court at the 11th hour, setting John - Sharon's brother - on a life of campaigning and advocacy following the Whelan family's experience of the justice system.