The establishment of a judicial inquiry to investigate events that have already been investigated by a judicial inquiry is unprecedented in British legal history. Given the success with which the findings and methodology of the Widgery Tribunal have been attacked in recent months, however, it was virtually inevitable that a new inquiry would be established into the events of Bloody Sunday. Nevertheless, it cannot be taken for granted that the inquiry will automatically be more successful in finding the truth which proved so elusive for the Widgery Tribunal. Not only will the inquiry face the daunting task of investigating those same events 26 years later, but it will have to wrestle with the diplomatic niceties of being seen to reach conclusions which contradict those of a judicial tribunal chaired by a former Lord Chief Justice of England and Wales.

The essential factors which will be critical to its success in finding the truth and ultimately laying the ghost of Bloody Sunday to rest concern its composition, status and powers.

The inquiry's composition is vital to the whole question of public confidence in its independence and impartiality. It will also impact significantly upon the manner in which the inquiry sets about its task. An inquiry composed of an English judge sitting alone would be forever operating under the shadow of the Widgery Tribunal. There would always be the suspicion that such an inquiry was naturally predisposed towards the avoidance of conflict with the Widgery conclusions.

Accordingly, the inclusion of the two Commonwealth judges is a bold and necessary step. This will be the first occasion in which non-UK judges have been used by the British government to re-examine the findings of a tribunal of inquiry established by a previous British government.

Nevertheless, their presence will be vital not only in securing public confidence in the inquiry's outcome, but also in avoiding the appearance of any unseemly conflict between two inquiries chaired by British judges.

Closely allied to the composition of the inquiry is the issue of its status and powers. The fact that it has been established under the Tribunal and Inquiries (Evidence) Act, 1921 means that it has exactly the same status as the Widgery Tribunal. It has all the powers of the High Court in respect of compelling witnesses to attend and submit to cross-examination.

It can compel the production of documents and generally inquire into the events of Bloody Sunday as if the Widgery inquiry had never happened. This is highly significant because it means that the new inquiry will be more than a reassessment of the Widgery findings in the light of the new evidence.

All of the witnesses who appeared before the Widgery Tribunal can be examined and cross-examined again. Undoubtedly the question of immunity for the soldiers from criminal prosecution will also arise. Ultimately this will be a matter for the tribunal in consultation with the Attorney General.

However, given the fact that the families of the victims are looking for the truth as opposed to retribution, it is unlikely that this will pose any problem. The predominant interest in establishing the full truth would be served by granting immunity.

In the final analysis the success of the inquiry will be determined by the extent to which it can convince that it has established the full truth about Bloody Sunday. This, in turn, will be dictated largely by its terms of reference and the manner in which it sets about its task.

The fact that it will sit mostly in public is a useful start in this respect. Less certain are its terms of reference which are: "to inquire into the events of Sunday 30 January 1972 which led to loss of life in connection with the procession in Londonderry that day, taking account of any new information relevant to events on that day".

Apart from the bit about new evidence these are identical to the terms of reference of the Widgery Tribunal. It is worth remembering, therefore, that one of the key flaws in the Widgery Inquiry was its decision to interpret its terms of reference as being limited to what happened on the day of Bloody Sunday itself.

This precluded an examination of the vitally important issue of political involvement in the planning of Bloody Sunday and the extent to which policy and planning decisions taken at a high political and security level were directly responsible for the deaths and injuries.

It also resulted in the bizarre failure to address the shootings which resulted in the wounding of 14 civilians. If the new inquiry adopts a similarly myopic interpretation of its terms of reference it will fail utterly to discharge its onerous responsibility.

It is also critically important that the inquiry should recall the soldiers who gave evidence at the Widgery Inquiry. My own research has revealed that the thrust of the Widgery Report was fatally flawed by virtue of its uncritical reliance on the evidence of the soldiers.

Lord Widgery felt able to base the tribunal's conclusions on the testimony of the soldiers on the ground that they had given their evidence "with confidence and without hesitation or prevarication and withstood a rigorous cross-examination without contradicting each other".

What the tribunal did not reveal was that on the night of Bloody Sunday those same soldiers had given statements to the Military Police which conflicted in many material respects with the statements that they proffered to the tribunal. The changes, which had clearly been made with the benefit of legal advice, were aimed purposefully at ironing out inconsistencies among the soldiers' versions and to protect some of them against possible criminal charges of murder or attempted murder.

Not only did the tribunal conceal the existence of these original statements but it failed in its legal and moral duty to subject the soldiers to a rigorous cross-examination on the basis of the discrepancies between them and the sworn testimony offered by the soldiers at the tribunal.

Had such a cross-examination taken place it is inconceivable that the Widgery Tribunal could have based itself with such confidence on the evidence of the soldiers. Instead of exposing the truth, therefore, it would appear that the Widgery Tribunal actually played an instrumental role in preventing the full facts from being discovered. It is essential, therefore, that the new inquiry should recall these soldiers and give them an opportunity to tell the truth once and for all.

If the inquiry does ultimately succeed in establishing the full truth about what happened on Bloody Sunday and, just as importantly, how it was allowed to happen, it will make a major contribution to remedying one of the most acute nationalist grievances in Northern Ireland. It is unlikely, however, that it will go the whole way and establish why justice was not done 26 years ago.

Prof Dermot Walsh, professor of law at the University of Limerick, is the author of The Bloody Sunday Tribunal Of Inquiry: A Resounding Defeat for Truth, Justice and the Rule of Law. This report was the basis for the Irish Government's submission to the British government for a new inquiry into Bloody Sunday.