It had always been claimed the dead were hit by fire from ground level when paratroopers opened up on an anti-internment civil rights march in the city 25 years ago.
Now it appears that soldiers on duty on the walls overlooking the Bogside said they fired as well.
They claim they were fired on, and a local radio ham has produced a recording of Army transmissions, while a Londonderry doctor who attended some of the post-mortem examinations says three of the victims were killed by bullets which appeared to have been fired downwards at a 45-degree angle. Dr Raymond Maclean who was on the march was never called to give evidence at a public tribunal.
A new book also casts doubt on the independence of the official inquiry into the killings on 30 January 1972, which far from fading into the realms of history continue to have a huge significance for republicans.
The question of how the authorities handle killings by members of the security forces, in this and many other cases, remains a live issue and is seen as one of the most controversial in the field of justice.
Only this week there were criticisms of allegedly preferential treatment of a soldier, Lee Clegg of the Parachute Regiment, whose murder conviction was, unusually, referred back to the courts for review.
The Bloody Sunday killings were formally investigated by the then Lord Chief Justice, the late Lord Widgery.
His finding that the firing of some paratroopers had "bordered on the reckless" brought a deluge of criticism and allegations that it was a "whitewash" rather than an honest attempt to find out how 14 people came to be shot dead by British soldiers.
The Government originally claimed that all or most of the accused were gunmen or nail-bombers. But Lord Widgery recorded that no one except soldiers gave him evidence of seeing firearms or bombs; that none of the many photographs of the events showed guns or bombs; that no guns or bombs were recovered; and that no soldiers were injured by guns or bombs.
He concluded, however, that while none of the deceased was proved to have a gun or bomb when shot, there was a strong suspicion that some had earlier fired guns or handled bombs.
A new book, Eyewitness Bloody Sunday by Don Mullan, cites an official Home Office document, newly released by the Public Record Office, which lends support to the contention that Lord Widgery approached his findings with a view of blackening the dead and defending the soldiers' actions.
The book also says that three of the dead were shot from the city walls - Michael McDaid, aged 20, John Young, 17, and William Nash, 19.
The document records a meeting between Lord Widgery and a Home Office representative - presumably a minister or senior official - as the Lord Chief Justice was finalising his report. A hand-written note on the document records: "LCJ will pile up the case against the deceased ... but will conclude that he cannot find with certainty that any one of 13 was a gunman." (One of the 14 died later from his wounds).
The rest of the memorandum shows that the smallest details were together examined by Lord Widgery and the Government.
For example, the Home Office recorded its opinions about the performance of army officers - "Brigadier MacLennan loyally covered up for his subordinates, but Colonel Wilford's activities surely need some explaining."
The former Catholic Bishop of Derry, Dr Edward Daly, said of the Widgery report: "I was aghast by it, by the fact that the British Lord Chief Justice would not acknowledge the innocence of the victims and made a rather feeble attempt at exonerating those who actually pulled the trigger.
"But even though Widgery did engage in a whitewash, the evidence of the Paras was taken apart by our lawyers, and I think it was shown up as the fabrication that it was."
Tony Doherty, whose father was one of the dead, said: "It is clear that the Widgery team was stacked in favour of the Army's version.
"There was a spoken or unspoken conspiracy hatched in the upper echelons between Whitehall mandarins and the Widgery tribunal.
"What is needed and what we have been demanding for a number of years is a truly independent inquiry by international solicitors, recognised by the British and Irish governments."Reuse content