Proposals offering immunity from prosecution in return for information on Troubles murders are to be considered at all-party Haass talks in Belfast this week.
A paper outlining four models of immunity had been circulated to the parties by academics Dr Kieran McEvoy and Dr Louise Mallinder.
The options range from a unilateral end to prosecutions – as suggested by the Attorney General John Larkin – to targeted immunity for selected individuals in return for information.
It is understood that some form of truth investigation which had the power to offer limited immunity from prosecution is the most likely model to attract support.
At a Press conference yesterday, Dr Haass was asked directly if the issue of immunity from prosecution was under consideration.
He said: "Dealing with the past presents a very detailed and intricate set of issues. There is a multiple consideration from the personal to the human, to the legal to the historical."
He added: "Balancing it and trying to get as full a picture of what really happened is obviously in everyone's interest. What sort of incentives or mechanisms we might use, again will be on the table this week."
Alliance MP Naomi Long has already given her backing to a limited immunity model.
She said: "I have already gone on the record in the past to talk about issues around limited immunities and how that has worked in previous phases of this process and how it might be able to be used in future phases, but I think that everything is still to be discussed."
Jeffrey Donaldson of the DUP said: "We have made it clear both in public and in private that we are opposed to amnesties for terrorist murder."
However, he added "limited immunity is a separate concept".
Last month Attorney General Mr Larkin suggested that all inquests, investigations and prosecutions for events before the signing of the Good Friday Agreement in 1998 should be set aside. However, his suggestion was instantly dismissed by many politicians and victims.
But since then some have told the Belfast Telegraph that it was the manner and detail of Mr Larkin's proposal which had been rejected, along with the sweeping immunity he proposed.
All the parties have met Professor McEvoy and Dr Mallinder to discuss the proposals and, Dr Mallinder said, "so far the parties have been putting fairly detailed and technical questions to us about how it would work. They are not rejecting the ideas out of hand, and that is why we prepared this latest paper for them".
Limited immunity has already been granted here before. For instance, IRA members giving information on the location of the bodies of the Disappeared were given immunity.
When paramilitary weapons were being decommissioned members of terrorist groups were given permits to move them which guaranteed them freedom from arrest, and the authorities undertook not to prosecute anyone on the basis of clues left on the weapons themselves.
Yesterday Dr Haass told parties to prepare for "an intense two weeks of deliberations and negotiations".
He will meet each of the five Executive parties three times this week, once on each of the topics he has to consider, and also intends working through the weekend.
Legal guarantees aren't a new idea
Analysis by Liam Clarke
The issue of immunity from prosecution in return for information is not a new one.
We have seen it used at the Bloody Sunday Tribunal, when witnesses were legally guaranteed that they could not be prosecuted on the basis of their own evidence provided it was truthful. It was used to help gather information on the location of the bodies of the Disappeared and it was used to help get loyalist and republican weapons put beyond use.
The most interesting precedent is a little older – the Cameron Commisison. It was set up by Terence O'Neill, a unionist Prime Minister at Stormont, in 1969. Its remit was to probe the causes of the violence which hit the streets of Northern Ireland after October 1968, the very start of the Troubles.
It guaranteed that "no statement made to the Commission of Enquiry, whether orally or in writing, will be used as the basis of a prosecution against the maker of the statement or for the purpose of prosecution of any person or body of persons".
This went further than the Saville Inquiry, which offered immunity only to the person making the statement. This led some witnesses to refuse to answer some questions for fear of incriminating others. For instance Martin McGuinness, now the Deputy First Minister, refused to give the locations of IRA arms dumps.
Under this option the tribunal would be able to target those to whom it offered immunity. This happened in the more recent inquiry into the death of Baha Mousa, an Iraqi hotel worker, after a beating from British troops.
When we start to look at precedents like the Cameron and Baha Mousa inquiries, objections to the idea of amnesty may weaken. It could be replaced by a system in which immunity could be offered in a focused and targeted way.