The collection of mobile phone data used by Gardaí as part of efforts to convict Graham Dwyer, and the Irish law which allowed the practice to take place, were contrary to EU law, a senior judicial adviser at the European Court of Justice (ECJ) has said.
The Advocate General's advice will be considered by judges in the appeal which could have a far-reaching impact on how policing authorities throughout the EU gather evidence. A verdict is expected next year, according to The Irish Times.
The ECJ case arose after Dywer challenged the Irish law which allowed for the retention of his phone data by Gardaí, which the Irish Supreme Court referred on to Europe.
In 2015, Dwyer was convicted for the murder of Elaine O'Hara in 2012, with mobile phone data making up a key part of the prosecution's case. Dwyer has also lodged a separate appeal to his conviction with the Irish courts.
A hearing in September heard representations from a number of EU member states, including Ireland, calling for less restrictive rules on data retention, arguing that such limitations would hinder the work of police forces. Similar issues from French and German courts are also being considered as part of the case.
On Thursday morning, Advocate General Campos Sánchez-Bordone stated previous case law demonstrates that "general and indiscriminate" retention of mobile phone data "is permitted only in the event of a serious threat to national security".
Dwyer's legal representative, Remy Farrell SC previously told the ECJ hearing that the Irish law allowing phone data to be kept for two years was "extreme", claiming it allowed mobile phones to be used as "personal tracking devices".
