A man is being questioned by Gardaí in Dublin in connection with the murder of Dean Johnson in Clondalkin in August 2013.
A 31-year-old man was arrested yesterday and was taken to Lucan Garda Station for questioning.
He can be held for up to 3 days.
A woman, also aged 31, was also arrested in relation to the investigation yesterday.
She has since been released without charge.