By Ann O'Loughlin

A lawyer who reviewed the UK's anti-terror laws has told the High Court the use of data retained by telecommunications providers was of "crucial importance" to the investigation of serious crimes.

Barrister David Anderson QC who was the UK's Independent Reviewer of Terrorism Legislation said that the retention and use of data including telephone traffic records by British police and intelligence agencies had been vital in the prevention and detection of terrorism, cyber crimes, human trafficking, child abuse, and in catching serial killers.

Mr Anderson, who compiled a report into the use of communication data by police and others in the UK, was giving evidence on the fifth day of an action brought by convicted killer Graham Dywer, aimed at having provisions of Ireland's data retention laws struck down.

In evidence Mr Anderson cited examples where data retention was used by the UK police when investigating serious crimes.

One example where retained data was used was during South Wales Police's investigation into Lostprofits singer Ian Watkins.

Watkins was jailed for 29 years after he pleaded guilty in 2013 to offences including the sexual assault and attempted rape of two infant children, whose mothers were also convicted.

In his action, Dwyer claims the 2011 Communications (Retention of Data) Act, which allowed Gardai obtain and use data generated by Dwyer's mobile phone during his 2015 trial for the murder of childcare worker Elaine O'Hara breached his privacy rights.

The material obtained under that Act should not have been used at his trial, he claims. Dwyer argues the 2011 Act was introduced to give effect to the 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.

Dwyer's 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 as well as the EU Charter have been breached.

Dwyer (45) denies killing Ms O'Hara, and his appeal against his conviction is pending before the Court of Appeal.

His application is opposed.

Mr Anderson, in reply to Brian Murray SC for the State parties, said when compiling his report he spoke to various groups including police forces and NGOs inside and outside the UK.

His conclusion is that retained data can be of vital importance in a number of ways to investigators, including where the location of phones can be identified at the last place a murder victim was seen, or help to track the movements of an operational phone whose owner is unknown.

It can also identify premises of interest, or trace the movements of a suspect, establish innocence and locate highly vulnerable persons.

Mr Anderson said he did not believe there is any effective alternative to a general data retention regime.

Targeting specific areas or the "quick freezing" of data relating to specific persons after they become subject to suspicion would not work.

He also said that after the courts in Germany and the Czech Republic struck down their data retention laws a large number of criminal investigations could not be solved.

Also giving evidence to the court yesterday (Tues) was defence expert Professor Michael Clarke. In reply to Sean Guerin SC for the State, Prof Clarke said he would not classify data retention as a form of surveillance.

The retention of data without anyone doing anything with it he said was "inert." In order for any form of surveillance to occur somebody would have to sift through the material and obtain a certain degree of information about a person or persons, he said.

The action, before Mr Justice Tony O'Connor, continues.