There were serious failings in the original investigation into the murder of Clodagh Hawe and her three sons in Co Cavan nine years ago.
There were mistakes collecting vital CCTV, which led to two gardaí facing disciplinary action.
Crucial digital evidence, including a secret phone used by murderer Alan Hawe to access depraved and illegal pornography, was also missed.
The damning findings on the first investigation are included in a serious garda case review.
The details are included in a book by Clodagh's sister, Jacqueline Connolly, and are reported in the Irish Independent today.
Clodagh, along with her three sons, aged between six and 13, was brutally murdered by her husband Alan Hawe in their home near Ballyjamesduff in 2016. He then took his own life.
