Updated at 17.30

The High Court has heard convicted killer Graham Dwyer maintains his innocence over the murder of Elaine O’Hara.

The former architect is taking a legal action against the State over the use of mobile phone data in his trial.

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, 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.

He said that, in 2013, gardaí in the case asked for records for that phone only as far back as 2011 - as that was all that was open to them and as far as they could.

The court heard Dwyer’s phone data featured heavily in his garda interviews and questions were put to him about where his phone was pinging at certain times and places.

A reminder about the graphic nature of texts between Dwyer and Elaine O’Hara was also heard in court - including one text which read - **‘It's your fault I want to kill and you won't let me stab you’’.

The Judge was told Dwyer maintains his innocence for her murder and is appealing his conviction.

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