Eagleson described the situation on Guantanamo as "a mess" and said he had decided not to attend any of the pre-trial proceedings there.

"My overall feeling is a sense of betrayal from the US government and a sense of extreme frustration," he said. "They've botched every single part of this trial."

With 25 years having passed since the attacks, he said that while 9/11 was a constant presence in his own life, to the wider public it was "becoming a historical event".

"I think people just assume that we got Bin Laden, we're out of Iraq, the war in Afghanistan's over, and they just assume that chapter has ended."

When the trial does eventually start, at a military court at Guantanamo, it has been estimated that it will last about a year.

Professor Kasey McCall-Smith said the point of the pre-trial proceedings had been determining "what evidence gets in and what evidence doesn't get in".

"If that is agreed in advance, the trial can be more expeditious," she explained.

As the relatives of the victims prepared for another anniversary marking the death of their loved ones, Gerhardt said he was looking forward to a time that the trial was over and he no longer had to think about or travel to Guantanamo.

"It's a place I don't want to come back to. I want to live my life, enjoy my passions and my memories of Ralph," he said.

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