A report by former chief justice John Murray supports convicted killer Graham Dwyer's claim that Ireland's data retention legislation breaches European laws, the High Court heard.

The retired chief justice said in a report that the Communications (Retention of Data) Act 2011 amounts to mass surveillance of the entire population of the State and was contrary to EU legislation, the court was told.

The report was commissioned in 2016 in the wake of allegations journalists' records were wrongfully accessed by the Garda Síochána Ombudsman Commission (Gsoc).

Remy Farrell SC, for Dwyer, told Mr Justice Tony O'Connor that while they are the opinion of a now retired judge, they do tie into Dwyer's complaints about Ireland's indiscriminate data retention regime.

Mr Farrell was speaking on the second day of Dwyer's challenge against the Garda Commissioner and the State, aimed at having struck down certain provisions of the law that allow data from mobile phones be used by prosecutors during his trial for the murder of Elaine O'Hara. The State denies the claims and says that he is not entitled to any of the declarations he seeks.

Dwyer's complaints include that the 2011 Act does not provide for any independent person, such as a judge, to oversee such requests, to limit what is strictly necessary or ensure privacy rights are protected before the material is handed over.

It would appear the only persons who had oversight of the request in relation to his client were gardaí themselves, counsel said.

Dwyer claim's that certain provisions of the 2011 Act breach his privacy rights under the European Charter, Irish Constitution and rights under the European Convention on Human Rights. Evidence gathered under the 2011 Act should not have been used against him in his trial, Dwyer claims.

In 2015, Dwyer was sentenced to life imprisonment after the jury found him guilty of the childcare worker's murder.

He denies killing Ms O'Hara, and has challenged provisions of the 2011 Act, which allowed gardaí investigating her death to obtain and use mobile phone records during his lengthy trial.

His appeal against his conviction remains pending before the Court of Appeal.

Mr Justice O'Connor also heard evidence from Dwyer's solicitor, Jonathan Dunphy, concerning his statement supporting his client's challenge.

Questioned by Sean Guerin SC, for the respondents, Mr Dunphy accepted that there were strands other than the retention of mobile phone data that resulted in gardaí arresting Dwyer in October 2013

Mr Dunphy accepted that the criminal trial had been told that Dwyer had, in interviews with gardaí, volunteered personal and private information about his family and professional life.

The hearing continues.

Irish Independent