The Special Criminal Court will admit the evidence of a social scientist who told the trial of Lisa Smith that everyone who travelled to Syria in support of the Islamic State was a member of the terrorist group Isis.
Mr Justice Tony Hunt, however, said it is a matter for the court to decide whether Ms Smith joined Isis and Dr Florence Gaub's opinion, "doesn't bind us in any way."
Mr Justice Hunt said the court accepts that Dr Gaub, a director with the European Union Institute for Security Studies, is an expert who can help the court to understand concepts relating to Ms Smith's decision to travel to Syria following a call by terrorist leader Abu Bakr al-Baghdadi.
He said some of those concepts are "outside the normal ken" of the three judges of the non-jury court.
'Paucity of sources'
Dr Gaub has given evidence that the Islamic State or caliphate announced by al-Baghdadi was the same thing as the terrorist organisation Isis and that a person became a member of Isis when they joined it "actively with any type of act of support".
Such support, she said, could be a tweet, sending money, joining Isis-controlled territory or carrying out a terrorist attack. She said that a person does not need to pick up a gun to be a member of the terrorist organisation.
Mr Justice Hunt said the court will also consider Dr Gaub's evidence that people who travelled to the Islamic State, to make "hijrah", received preferential treatment including better housing, food and access to the internet.
He said Ms Smith's lawyers' argument that Dr Gaub had a "paucity of sources" to confirm what she was saying does not render her evidence inadmissible but may impact the weight given to it by the court when considering their verdicts.
Ms Smith (40), from Dundalk, Co Louth, an Islamic convert and former Irish soldier, travelled to Syria after terrorist leader Abu Bakr al-Baghdadi called on all Muslims to travel to the Islamic State.
She has pleaded not guilty to membership of an unlawful terrorist group, Islamic State, between October 28th, 2015 and December 1st, 2019.
She has also pleaded not guilty to financing terrorism by sending €800 in assistance, via a Western Union money transfer, to a named man on May 6th, 2015.
Dr Gaub, who has already given evidence in person at the trial, has now left the country but will continue her testimony on Monday via video link.
