At the sitting of the Special Criminal Court, Det Sgt Shane Noone said he arrested O’Donovan at 17:07 local time on Friday and informed him he would be charged with the offence.
Solicitor Darragh Mackin said he had not taken instruction from O’Donovan as he was observing a strike over changes to criminal legal aid fees and was only appearing in court out of courtesy.
O’Donovan told Judge Patrick McGrath that he had “no representation at all”, and had asked for “the services of this gentleman beside me”, referring to Mackin.
O’Donovan was remanded in custody until Monday.
Law student Isobella Perrie Sullivan, 25, of Abbeylands Park in Clane, County Kildare, appeared before a district court on Friday charged with possession of explosives in connection with the same incident.
Her solicitor said she had been asked to take a bag to the north, and had not been aware what was in it.
Perrie Sullivan was granted bail but remains in custody ahead of a further bail hearing on Monday.