Sources say that it is likely that Cullen will now have to go into the Witness Protection Programme after finishing a three-and-a-half-year sentence, which was imposed on him yesterday at the Special Criminal Court.
A source told the Herald: "The raids that happened at the weekend on three homes were the first of a number of additional searches that will take place in light of new information provided to gardai.
"Mr Cullen is now in a very precarious position and will require to be on protection in jail and will most likely have to go into the Witness Protection Programme when he is finished his sentence."
It is understood that no fireams were discovered during the raids at the three houses in Balbriggan last Saturday as the investigation into Butterly's gruesome murder continues.
Yesterday, at the Special Criminal Court, David Cullen (30), of Brackenwood Ave, Balbriggan, pleaded guilty to the unlawful possession of a 9mm calibre Beretta model 9000s semi-automatic pistol at the Huntsman Inn at Gormanston, Co Meath, on March 6, 2013.
Last year, Cullen and his co-accused Edward McGrath (32), of Land Dale Lawns, Springfield, Tallaght, Dean Evans (22), of Grange Park Rise, Raheny, and Sharif Kelly (43) of Pinewood Green Road, Balbriggan were charged with the murder of Peter Butterly. They all deny the charge.
Butterly, a 35-year-old father of two, was shot dead in the car park of the Huntsman Inn at Gormanston, Co Meath, on March 6, 2013.
Ms Una Ni Raifeartaigh SC, for the State, said that Cullen's plea was acceptable to the Director of Public Prosecutions and a nolle prosequi - a decision not to proceed - would be entered on the count of murder.
The court heard yesterday that David Cullen had made contact with gardai through his solicitor and indicated a willingness to give evidence on behalf of the prosecution.
On June 27, Cullen gave a voluntary statement giving details of the offences and the involvement of certain people.