Eamon Bradley, 28, a Muslim convert from Melmore Gardens in Creggan, is on trial at Londonderry Crown Court.
The 28-year-old denies six charges, including receiving training in the use of guns and grenades in Syria.
The offences are alleged to have happened between 31 March and 29 October 2014.
On the fifth day of his trial, the court heard transcripts of police interviews where Mr Bradley was asked if the rebel faction he allegedly trained with had a flag, and if he could describe it.
Mr Bradley told police he could not describe the flag and, when asked why, said he could not remember it.
A defence barrister asked a detective constable if that had sparked an alarm bell, given that Mr Bradley had returned home from Syria just one week previously.
According to his barrister, Mr Bradley went on to tell police that he believed that there was green in the flag, adding: "I might be describing another flag altogether."
An image of the defendant wearing combat gear sitting in the back of a vehicle was also referred to in court.
The court heard that Eamon Bradley told police he thought the vehicle was a tank, but said he did not know what sort of a tank it was.
The trial continues.
A Londonderry man accused of terrorism 'could not remember' the flag of a rebel group he allegedly trained with in Syria, a court has heard.