Graham Dwyer has won his legal action against the State and Garda Commissioner over the use of mobile phone data in his murder trial.
The former architect was convicted by a jury three years ago of the 2012 murder of childcare worker Elaine O’Hara.
Mobile phone data formed a huge part of the trial but Dwyer argued it shouldn’t have been used as it breached his rights.
The High Court has ruled that Irish laws - which allow for mobile phone data to be retained and accessed - breaches EU law.
He has already stated his intention to go to the Court of Appeal to challenge his murder conviction.
Additional reporting by Stephanie Rohan