Graham Dwyer "cannot escape" a court ruling that retained data generated by his mobile phone could be used as evidence against him during his trial before the Central Criminal for the murder of Elaine O'Hara.
Brian Murray SC for the State and the Garda Commissioner said telecommunication data from Dwyer's personal mobile phone was retained and accessed by the Gardai investigating Ms O'Hara's death under the 2011 Communications Act.
At the relevant time Ireland was mandated by the EU to have such an Act in relation to retained data in place for the investigation, prevention and prosecution of serious crimes.
Counsel said the European Court of Justice (ECJ) had in 2014 made certain adverse findings about the 2006 EU directive underpinning the 2011 Act.
Dwyer's lawyers applied to the judge presiding over his trial before a jury at the Central Criminal Court to have the retained data excluded from his 2015 trial based on the ECJ's decision.
The trial Judge Mr Justice Tony Hunt ruled against Dwyer and allowed the contested evidence go before the jury.
Counsel said it is the State's case in the High Court proceedings that the retention and use of Dwyer's data at his trial was lawful and a finding the Cork born architect "cannot escape."
Counsel was making submissions on the 10th day of Dwyer's action against the State and the Garda Commissioner aimed at having provisions of Ireland's data retention laws struck down.
Dwyer, who denies killing Ms O'Hara, claims the 2011 Communications (Retention of Data) Act, which allowed Gardai obtain and use data generated by his mobile phone during his 2015 trial for Ms O'Hara's murder breached his privacy rights.
Data obtained under that Act should not have been used at his trial, he claims. Dwyer argues the Act was introduced to give effect to a 2006 EU directive concerning the retention and use of data.
The European Court of Justice (ECJ) found in 2014 the directive was invalid and that position was further strengthened in subsequent rulings by that court in 2016. He claims the 2011 Act suffers from the same flaws identified by the ECJ.
In proceedings against the Garda Commissioner, and the State, Dwyer seeks various declarations that his privacy rights under the Irish Constitution, European Convention on Human Rights and the EU Charter have been breached.
During his submissions Mr Murray also told the court that no evidence had been given by the ECJ in its decisions about data retention regimes as to how alternatives to a general data retention system would work.
Counsel said the 2016 ECJ rulings did not refer to any jurisdictions where alternative retention regimes which would deemed as less invasive on privacy rights had been attempted or tested, he added.
The action continues and is expected to conclude later this week.