The Hillsborough disaster is "seared into the memories" of everyone affected by it, the coroner has told jurors hearing the fresh inquests into the deaths of the 96 fans who died.
In an opening statement, Lord Justice Goldring described the "terrible crush" that led to "the worst-ever disaster at a British sports stadium".
The disaster unfolded on 15 April 1989 during Liverpool's FA Cup semi-final against Nottingham Forest.
The hearing could last a year.
The names of each victim were read aloud at the coroner's court in Warrington by Christina Lambert QC, counsel to the inquests, before the jury of seven women and four men were sworn in.
The coroner said the original verdicts of accidental death in March 1991 were quashed in December 2012, after the Hillsborough Independent Panel delivered its final report earlier that year.
'Pressure in pens'
"A new inquiry was needed," he said.
"In doing so we are not concerned with whether what was decided at the previous inquiries was right or wrong."
The coroner said the inquests would "investigate the disaster as a whole and consider the experiences of each of the 96".
Outlining the events at Sheffield Wednesday's Hillsborough ground, he said: "Around the time of the kick-off, a terrible crush developed in two pens, within the... terrace at the west end of the stadium - the Leppings Lane end.
"That's where the Liverpool fans were standing.
"The pressure in the pens built up. Many of those in the pens suffered terrible crushing injuries."
He said that witnesses' memories "will inevitably have faded" in almost 25 years since the disaster.
Reports of crushing
The coroner added: "As part of your task, you will, I anticipate, have to consider the underlying circumstances which contributed to the cause of these deaths, whether opportunities were lost which might have prevented the deaths or saved lives."
The jury was told 500,000 documents and pieces of evidence have been disclosed to the legal teams so far.
The coroner recalled a crushing incident at Hillsborough in 1981, in which 38 people were injured.
It was relieved when gates in the fence between the terrace and the pitch were opened.
The central pen in the Leppings Lane terrace was given a capacity of 2,200 after that incident, but there was no means of counting how many people entered a particular pen, the inquest heard.
Counters on the banks of turnstiles only recorded how many people entered the ground.
'Couldn't be heard'
"What the monitoring system could not say was how many people had gone into pens three and four, or whether the maximum capacity of these pens had been reached," said the coroner.
"To know that would require police officers or stewards at the tunnel entrance with handheld counting devices, and that did not happen on 15 April 1989."
Lord Justice Goldring also said that some police officers could not communicate when using their mobile radios, or they could not be heard.
The coroner recalled reports of crushing in 1988 at another FA Cup semi-final between Liverpool and Nottingham Forest.
"Some fans who attended the match later gave accounts of there being pressure and crushing within the Leppings Lane terraces," he said.
Authorities thought the operation successful and "later modelled their plan for 1989" on the 1988 tie, he added.
Jurors heard that before the 1989 semi-final, Peter Robinson, secretary of Liverpool, suggested the club's supporters should not be allocated the Leppings Lane end.
'Open the gates'
Ch Supt David Duckenfield, who was in charge on match day, had been promoted on 27 March and given responsibility for Hillsborough over a more experienced officer.
Lord Justice Goldring said: "Whether that was a sensible decision may be something for you to have to consider."
He reminded the jury that Ch Supt Duckenfield told Graham Kelly, the chief executive of the Football Association, at 15:15 that a gate had been forced open, allowing fans to enter the ground.
In fact, the officer had ordered: "Open the gates".
The coroner said: "There is no question of Gate C having been forced.
"This early account resulted in some seriously inaccurate reporting of events. You will want to consider why Ch Supt Duckenfield said what he did."
'Wisdom of hindsight'
The jury will have a one-day site visit to the stadium.
The inquests are being held in a purpose-built courtroom, the biggest in England and Wales, in an office building in Birchwood Park, Warrington.
The hearing will not sit in the week of the disaster's 25th anniversary.
Jurors were reminded media reporting of the anniversary was "not evidence".
The coroner also warned about the "wisdom of hindsight", adding: "Beware, too, of applying the standards of 2014 to events which happened in 1989."
The inquest was adjourned until Wednesday.