The prospect of IRA decommissioning in the short term may have been extremely remote, but it must now be considered a complete non-starter in the wake of Rosemary Nelson's killing in Lurgan yesterday.
Any violent incident constitutes a setback for peace efforts in Northern Ireland but the death of a lawyer with a high profile on issues of human rights and alleged collusion between the security forces and loyalist paramilitaries plunge the process into crisis.
In the words of the SDLP deputy mayor of Craigavon, Ms Dolores Kelly, Ms Nelson "took the issues nobody else wanted to touch".
She was very active in highlighting the need to investigate claims of collusion, and there are disturbing and sinister parallels between her death and that of the Belfast-based solicitor, Pat Finucane. The London Metropolitan Police was supervising an investigation into complaints by Ms Nelson about threats allegedly made to her by the security forces.
Fresh claims about the extent of collusion that underlay the Finucane killing had begun to circulate, with some observers forecasting that a major scandal was about to be revealed. It was precisely the kind of issue Ms Nelson would have spoken out on, in her usual forthright manner.
That may be one of the reasons she was killed - or so many nationalists will suspect.
The killing will bring gloom and depression to anyone seeking to promote the normal rule of law and respect for the rights of citizens and their legal representatives in Northern Ireland.
Naturally, there is shock and outrage in the US, where most of the Northern political leaders are gathered for the St Patrick's Day events. Up to yesterday, there had been a fair amount of hope that a resolution of the decommissioning impasse could be attained.
Drafts of possible IRA statements were being circulated by mediators, whereby the republicans would declare that, although an arms handover was not being contemplated, their essential aim was to see the guns removed from Irish politics.
Attention was focusing once more on the hint of flexibility on the weapons issue given by Mr David Trimble in his Nobel Prize acceptance speech, when he said: "I have not insisted on precise dates, quantities and manner of decommissioning. All I have asked for is a credible beginning. All I have asked for is that they say that the `war' is over."
But for the present, these efforts must be considered on hold.
Ms Nelson's death has revived the old fears and suspicions, especially among republicans. Conspiracy theorists, with their claims that a counter-insurgency programme of assassination and intimidation has been in operation over many years, will get a more respectful hearing than before.
The key figures in the peace process have had to cope with similar crises in the past. Somehow or other the problems have always been overcome. The difficulty now is that time is limited - Good Friday is the psychological target-date but the executive would need to be set up earlier in the week, probably on March 29th or 30th, to allow Westminster to pass the necessary legislation completing the transfer of powers before Easter.
President Clinton is said to have been consulting widely with the two governments and particularly with senior Irish-American politicians on his approach to discussions with Northern politicians this week. The Irish-American lobby has a level of influence with republicans that neither Dublin nor London enjoys.
Conciliation efforts will resume despite a definite drop in the political temperature. Some of the participants, at least, will not want to give Ms Nelson's killers the additional satisfaction of derailing the peace process.
Dublin sources, in particular, have been quietly confident up to now that the arms impasse can be broken and even yesterday's outrage will not undermine that fundamental conviction.
The confidence Dublin feels about resolving the dispute is combined with a certain amount of apprehension as well as a deep awareness of the political and security risks involved in the current process. Despite the fact their parents or grandparents might have been active in the War of Independence the present-day republican movement is a closed book to most Dail politicians.
However, while negotiations with Mr Gerry Adams and Mr Martin McGuinness may not always be easy, a level of trust has been built up over recent years. Statements by Sinn Fein leaders that they cannot "deliver" on decommissioning are accepted at face value by Dublin. That does not stop the effort to persuade the republican movement that this issue cannot be left in abeyance. The longer it remains unresolved, the more uneasy public opinion in the Republic will become.
Dublin accepts privately, though, that there are no weapons on the table - although other imaginative ways of narrowing the gap between "decommissioning" and "out of commission" could still be found and the long-awaited report from Gen de Chastelain is crucial.
The lack of "hardware" could be compensated and even outweighed by an IRA statement which constituted a form of closure on the armed struggle, however conditional and qualified. Sinn Fein is on the threshold of government and it would not be acceptable, in democratic terms, if the threat of renewed violence remained. Even if an IRA statement is forthcoming, there will be many sceptics and cynics to dismiss it and to criticise those politicians who decide to take "one more risk for peace". The counterargument is that yesterday's killing shows the alternative to making that leap of faith.