The police commander in charge at Hillsborough on the day of the 1989 disaster agreed his failure to close a tunnel was the "direct cause" of the deaths of 96 Liverpool fans.
David Duckenfield, 70, told the Hillsborough inquests he "froze" before ordering the opening of an exit gate to relieve congestion at the FA Cup semifinal between Liverpool and Nottingham Forest.
The retired police chief was responding to questions from barrister Paul Greaney, representing the Police Federation, during his sixth day of evidence at the new Hillsborough inquests in Warrington, Cheshire. New inquests are being held after the original verdicts of accidental death were overturned.
Up to 2,000 fans entered Gate C, with many heading straight for a tunnel in front of them which Duckenfield had not ordered to be closed and then on to the already full central pen on the terrace which led to the fatal crushing.
Duckenfield accepted that people died in a crush that would not have taken place if fans had been prevented from going down a tunnel into the central pen.
In previous testimony to the inquest counsel, Duckenfield said of his decision to close the gate: "It was a momentous decision and your decision is such that you do not think of the next step. My mind for a moment went blank."
Asked again if he had "froze," Duckenfield told Greaney: "It appears to be a distinct possibility."
Duckenfield agreed with Greaney's questioning that he "failed to recognise that there was a need to close that tunnel" and "that failure was the direct cause of the deaths of 96 persons in the Hillsborough tragedy."
The inquests have heard that Mr Duckenfield told the 1989 Taylor Inquiry into the disaster that he had made the right decisions on the day but he now accepted that he had made errors -- some of which were "grave."
He has told the jury that his serious failings were due to his lack of experience and that others also played their part in the cause of the deaths.
He said he was unaware of the geography of Sheffield Wednesday's ground, this being his first match in charge.
Asked if he understood the consequence of his failure to act, Duckenfield said: "I did not think of it on the day, sir, because of the pressure I was under."
Duckenfield agreed with Greaney that it was "totally unacceptable" that a match commander "did not have a grip on the geography of that ground sufficient to enable you to understand the consequences of your decision making."
He also accepted that when giving evidence to Lord Justice Taylor it appeared that he was aware that the congested Leppings Lane turnstiles did lead to the central tunnel.
Duckenfield said he did not want to go into detail about his "personal circumstances" -- he has previously said he suffered post-traumatic stress -- but he may have been "confused" when giving evidence in 1989.
The retired chief superintendent of South Yorkshire Police denied that he failed to offer "any true leadership" on the day.
He accepted that officers under his command received no instructions to stop the filling of the Leppings Lane terrace pens.
"Sir, I think it is fair to say that we were all in a state of shock," he said.
Duckenfield agreed with his barrister that it was only in recent times that he had been able to come to terms with his mistakes and make the admissions he made to the jury last week.
Asked whether he had found it easy to admit his "professional failings which led to the deaths of 96 innocent men, women and children", Duckenfield said: "It has been the most difficult period of my life."
Information from Press Association and The Associated Press was used in this report.