Dwyer was convicted in 2015 for the murder of Elaine O’Hara

Lawyers for convicted murderer Graham Dwyer have begun his legal action against the State over mobile phone records.

Dwyer was convicted in 2015 for the killing of Elaine O’Hara, in what was of the biggest trials ever in the country.

Mobile phone data formed a huge role in Dwyer's trial.

The jury found the former architect, with an address in Foxrock in Dublin, had stabbed childcare worker Elaine O'Hara for his own sexual gratification.

He is appealing his conviction and, ahead of that, he is taking a legal action against the State - saying his right to privacy was breached because of laws surrounding how such phone data is retained and accessed.

In his opening address, Graham Dwyer's barrister, Remy Farrell, said the phone at the centre of this case is Dwyer’s work phone, and how it connected with two other phones to show his movements.

Dwyer is not present in court for the hearing, but his father and investigating gardaí are.