He claimed that Dunne later said that, if he agreed to do "something handy" for him, the debt would be cleared. He told Warren, a bricklayer and former soldier, to find a working consaw.
The accused claimed he was acting under duress and had been told by Dunne that if he didn't cut open a Chubb security jeep with the consaw on the morning of the raid, he would be "on top of Marlo" or "sent to God's house".
Warren finished his testimony yesterday, but Judge Patrick McCartan told the jury that the State wished to call further evidence.
Warren, of Belclare Crescent, Ballymun has pleaded not guilty at Dublin Circuit Criminal Court to conspiring to steal cash from Chubb Ireland at Tesco supermarket on Shackleton Road, Celbridge on Nov 2, 2007.
Detective Garda Adrian Mulligan said Warren told him on March 26, 2008 that there was "double-crossing" in the gang that tried to raid the cash-in-transit van and that he believed he was being left "high and dry".
Det Gda Mulligan said when he met Warren he said he believed a man named Michael 'Roly' Cronin had a grievance with him due to him being in Dunne's gang.
He also said he had concerns about a man acting suspiciously by the shops outside his home the previous night.
He said Warren told him he had worries about Dunne and the Bradley brothers.
"He believed he was now in a vulnerable position and believed he was a target for both Cronin and Dunne."
Det Gda Mulligan said Warren never told him at that time that he had been under threat in relation to the Celbridge raid or that he owed a debt for a car, even though he had "ample opportunity".
"He never told me because I don't believe the threat existed," Det Gda Mulligan said. He added that, when Warren became suspicious about the person outside his home, he came down to the garda station to report it the next day.
Garda Eamon Taaffe said that a week after Dunne was murdered in April 2010 he spoke to Warren and two other men who were sitting in a car outside Warren's girlfriend's home.
He said he spoke to Warren about the media coverage of Dunne's death, which claimed that Dunne was the boss.
Garda Taaffe said Warren replied: "Eamon Dunne was never the boss." He said he did not elaborate further.
Garda Taaffe refused to accept a suggestion from Ciaran O'Loughlin, defending, that his client had actually said, "Eamon Dunne was never my boss".
He agreed that he did not take notes of what Warren said at that time because it was just a general chat, but said he returned to the station an hour later and "entered the entire conversation into the pulse record".
Garda Cathal Connolly said he was at a funeral in Ballymun in November 2009 when he saw Warren approach Dunne and two other men, and have a conversation with them.
He said he saw Warren speak "briefly" to the same three men at the cemetery later that day.
The case continues.