The Bloody Sunday Inquiry proper opened in 2000 when formal public hearings began at the Guildhall in Derry.
In his opening statement on 27 March, Counsel to the Inquiry Christopher Clarke QC declared that the tribunal's task was to establish "so far as is humanly possible" the truth.
The most important issue for the families was whether or not soldiers would be obliged to give evidence in Derry without the right to remain anonymous.
The families and the inquiry lost this battle, and the subsequent legal battle to make the soldiers come to the city at all.
The Belfast-based newspaper the Irish News attempted to get around the ban and published the names of members of the Parachute Regiment.
A forensic report commissioned by the inquiry demolished a key finding of the 1972 Widgery report which found that many of those shot dead had handled weapons.
Shortly before the hearings began, the Ministry of Defence admitted that 14 of the 29 rifles believed to have been fired on the day had been destroyed and another 10 had been sold. The MoD blamed computer error.
Eyewitnesses and survivors
The inquiry heard how marchers attempting to rescue a wounded teenager dropped him in panic, fearing they too would be shot.
The inquiry also heard that Father Joseph Carolan, a priest present on the march, had been delayed from aiding the wounded by a soldier who had held a gun to his head.
Other witness accounts suggested that the army had no justification whatsoever for shooting dead 17-year-old Jackie Duddy, the first victim of the day.
In June 2000 the inquiry heard that one victim had his hands in the air before he was shot.
One of the men injured on the day recorded his testimony of what happened, an audio tape played decades later to the inquiry.
The first of an expected 1,500 live witnesses took the stand on 28 November 2000.
One of the first witnesses admitted he had thrown stones at soldiers but believed that the first two people killed were not involved in the disturbances.
In one of the last statements of the year, a former Derry priest said that he would not have urged people to attend the march, had there been any signs that the IRA was going to attack the security forces.
Role of the army
One of the principle goals for the inquiry is to establish exactly what orders had been given to soldiers.
The Guardian newspaper reported at the time of the inquiry's opening that senior officers had endorsed a policy of shooting rioters.
The inquiry also heard that there were disagreements between the Army and the Royal Ulster Constabulary over how to deal with the march.
Early evidence also suggested that one of the soldiers may have broken live firing rules.
One soldier claimed that an officer had encouraged him and colleagues to get "a few kills". Two soldiers who checked the body of 17-year-old Gerard Donaghey found no explosive devices
These early allegations were revisited when a lawyer for the families claimed that the then second highest-ranking British Army officer in Northern Ireland supported a shooting policy.
The inquiry also heard that the police concluded that the first killing had been murder - but no soldier had been held to account.
Allegations emerged that the security plan had backing at the highest levels in London and Belfast.
On 27 November 2000, a lawyer for most of the soldiers acknowledged that innocent people had been killed.
Role of the IRA
Since 1972, the army has insisted that its soldiers came under fire first and that the IRA, Official, Provisional or both, was active on Bloody Sunday.
In April 2000, the inquiry heard that the Official IRA had fired six shots - but not until the army had started shooting.
This was followed by further allegations that Martin McGuinness, then a young Provisional IRA commander in the city, had also shot at the army - possibly sparking the violence. Mr McGuinness described the allegation as a "pathetic fabrication" but only later agreed to give evidence to the inquiry.
In September 2000 the IRA released a tape to the inquiry saying that it was a recording of a bugged conversation between army personnel on Bloody Sunday.
Army allegations that the IRA may have spirited away bodies of the dead were rejected in November 2000.
Later, a self-confessed IRA man told the inquiry that he would have turned to guns, if they had been available.