The Bloody Sunday Inquiry held public hearings on 116 days during 2001, clocking up more than 600 hours of evidence. The vast majority of the evidence was from eyewitnesses.
In August, the inquiry ordered the soldiers who had opened fire to return to Derry to give their evidence.
But in December, the Court of Appeal overruled the inquiry and accepted that the former soldiers would be in danger from dissident republicans should they return to Northern Ireland.
Lord Saville later said that he would not move the hearings from Derry and that the soldiers' evidence would be relayed by video link.
Eyewitnesses and survivors
One of the first eyewitnesses to take the stand in January 2001, Damien Donaghy, said that he finally felt exonerated because lawyers for soldiers had accepted he had not been throwing a nail bomb when he was shot.
A friend of Jackie Duddy, the first youth shot dead on the day, told the inquiry of how he was just feet away from the victim as he was hit.
A BBC journalist who witnessed Bloody Sunday told the inquiry that he saw no reason for live firing.
One of the most important witnesses was the retired Bishop of Derry, Dr Edward Daly. He told the inquiry that the marchers posed no threat when soldiers opened fire.
A man who said that he was shot in the back told the inquiry that he had only survived because he stooped at the right moment.
Much of the evidence of the year was similar in nature, adding up to a picture of a grave and chaotic situation on the day. One witness in April said that the soldiers' bullets had come like hailstones.
The former MP Bernadette McAliskey told of her "sheer terror". A former BBC journalist said that his initial report of soldiers facing a "fusillade of terrorists' fire" had been wrong.
Denis Bradley, a former priest who later became an intermediary between the IRA and British government, said that members of the organisation had talked to him about Bloody Sunday, but he could not break their confidence by naming them.
Role of the IRA
Yet again, the role of republicans came to the fore when the inquiry heard that there may be a "wall of silence" in Derry over what exactly members of the IRA were doing on the day.
The allegations persisted when a witness in February 2001 refused to name a man he said had fired at soldiers.
In March, the journalist Eamon McCann appealed to the Provisional IRA to give evidence, saying that they would damage the families' chances of establishing the truth if they did not take the stand.
One former civil rights activist confidentially named an IRA man who he said had provided assurances that gun men would stay away from the march.
On 2 May 2001, Martin McGuinness became the most important member of the modern republican movement to confirm that he had been an IRA commander on Bloody Sunday.
This move did little to dampen speculation about his role and in November a biography claimed that Mr McGuinness had taken part in IRA activity on the day.
In June 2001, a retired taxi driver said that he had seen the IRA move guns out of the Bogside before the march.
One Derry woman, Monica Barr, said that she saw a second civilian gunman firing from a flat close to where Father Edward Daly was trying to save Duddy.
Role of the Army
The inquiry re-opened on 15 January 2001 with the Ministry of Defence denying that it was trying to frustrate the inquiry.
In March the inquiry heard how one soldier had described the events as "a bad day's work".
Another witness told how he had goaded soldiers to shoot him in his fury following the first firing.
Michael Bradley told the inquiry he wanted to meet the soldier who had shot him to ask how he had slept with his conscience.
A former Times newspaper journalist said that he believed that the troops had not planned to open fire. But, equally, the security strategy may have been to practise a future tough operation to take control of "Free Derry".
In contrast, another witness said he saw a soldier shoot a fleeing man.
In May, the inquiry became mired in controversy when solicitors acting for the soldiers asked to be supplied with intelligence reports on witnesses.
Lawyers for some civilian witnesses said that their clients feared they would be branded as members of the IRA, without due foundation.
While the issue continued in the background through the year, Lord Saville said that he was only prepared to request intelligence files on witnesses who it was thought would be able to explain IRA thinking and activities on the day.