Lawyers for the State and the Garda Commissioner are to appeal the High Court's decision in favour of convicted murderer Graham Dwyer over the retention and accessing of his mobile phone data.

Dwyer won his action last year.

The High Court found Irish legislation allowing such data to be retained and accessed for the prevention, detection, investigation or prosecution of a serious offence, breached EU law and the European Convention on Human Rights.

The High Court was told this morning that the State intends to appeal and intends to apply for a leapfrog appeal, which would allow it to bypass the Court of Appeal and go straight to the Supreme Court.

Mr Justice Tony O'Connor heard both sides were willing to consent to a stay on the declarations sought by Dwyer taking effect until the appeal is finally determined.

The parties will return to court later today when the judge will finalise his orders.

Dwyer was convicted by a jury three years ago of the 2012 murder of Elaine O'Hara.

Mobile phone metadata was an important part of the case, as it allowed the prosecution to show where Dwyer's phone was at certain times.

Gardaí were able to get the information under legislation brought in following a European directive later declared invalid.

Mr Justice O'Connor found the legislation allowing such data to be kept for the purposes of investigating serious offences was general and indiscriminate, and breached EU law.  

He said the Court of Justice of the EU had ruled that even the objective of fighting serious crime could not justify such an indiscriminate regime of retaining data.

He also ruled the system of accessing such data breached the European convention on human rights because there was no prior review by an independent authority before it could be accessed.

The judge said the chilling effect on privacy and the rights of free expression and association by actual, feared and mandatory surveillance could not be underestimated. 

But he said it was not an automatic consequence of his ruling that trials would collapse or that convictions would be quashed.  

He said Dwyer and others would still have to address the rules relating to the admissibility of evidence.

This evening, the High Court ordered that the enforcement of declarations in relation to the legislation on the retention and accessing of mobile phone data should be stayed until an appeal is lodged and until the first hearing before the court of appeal or the Supreme Court.

After that it will be up to the higher court to grant any further stays.

The court also recommended that the State pay Dwyer's legal costs in relation to the case.