The Rev Ian Paisley's right to keep secret the source of information for a speech in parliament about the Kingsmill massacre of 10 Protestants was defended in the High Court in Belfast yesterday.
Mr Jim Allister, lawyer for the DUP leader, said: "To allow the long arm of this court to reach into the chamber of the House of Commons to extract from an MP a source is unthinkable in terms of the historic and constitutional importance of parliamentary privilege."
Dr Paisley named 20 men he alleged were involved in the 1976 massacre in a speech in January, 1999. Three of them have applied for discovery of the security forces document on which he said he based his speech, so that they can bring libel proceedings.
At yesterday's resumed hearing, Mr Allister said the application was in breach of Article 9 of the Bill of Rights, which stated that a speech in parliament was not open to impeachment or questioning.
Mr Justice Sheil said he would deliver judgment later.