50 years ago today, the World Trade Centers twin towers debuted as the tallest buildings in the world. Standing at 1,368 and 1,362 feet, about 110 stories each, they surpassed the height of the Empire State Building, which until then was the tallest building in New York. The ceremonial opening of the twin towers in April,1973 followed seven years of construction and more than a decade of planning. The towers, which cost over a billion dollars to build, completely transformed 16 acres of Lower Manhattan into an international business hub. But, as most of you know, those towers were brought down in September 2001, when 19 militants associated with the Islamist extremist group al-Qaida hijacked four airplanes and flew two of them into the twin towers. The other two planes flew into the Pentagon, and one crashed outside of Shanksville, Pennsylvania. Nearly 3,000 people lost their lives in the attacks, with more than 2,700 of those deaths happening at the Twin Towers. Even though the towers are gone, the legacy of the World Trade Center and the people who died on 9/11 lives on as do the efforts to get justice for these attacks. In this episode, we wanted to examine where the case against the alleged accessories in the 9/11 attacks stands today. You might not have realized it but, five primary suspects accused of funding, training and supporting the attacks have yet to face trial more than two decades later. Theyve remained in U.S. custody since 2002 and 2003 and have been held at the U.S. military prison in Guantanamo Bay in Cuba also known as Gitmo for over a decade. The efforts to bring them to trial have been plagued with problems. But before we dig into those, lets get a quick rundown of who were talking about. The first suspect is Khalid Shaikh Mohammed, accused of having conceived and overseen the 9/11 plot. Then theres Walid bin Attash, also known as Khallad, who stands accused of training some of the hijackers in hand-to-hand fighting, researching flights to hijack, and testing U.S. security systems for air travel. The third suspect, Ramzi bin al-Shibh, is accused of organizing the hijacker cell and funding the attack. Ammar al-Baluchi is named in the charges as Abd al Aziz Ali. As suspect number four, he stands accused of providing money transfers to hijackers. The fifth suspect, Mustafa al Hawsawi, has been accused of helping the attackers with finances and planning. SEE MORE: The U.S. marks the 21st anniversary of the 9/11 terror attacksCollectively, they face charges of conspiracy, murder in violation of the law of war, and terrorism. The defendants were arraigned in May 2012. More than a decade later, talks have gone from a prospective death penalty to attempts at a plea deal to have them serve life in prison instead. Robert Goldman is a professor of law at American Universitys Washington College of Law. He formerly lent his expertise to the UN, working in the field of human rights and fundamental freedoms while countering terrorism. "I think it's going to be dragged on and on and on," Goldman said.Goldman spoke with Scripps News about why the case has been stuck in the pre-trial phase. One of the biggest reasons, he says, is the "enhanced interrogation techniques" used to get information from the suspects. The phrase has come to be known as a euphemism for torture. "The problem is you got dirty hands. These people were tortured at the hands of agents of the United States. And now those same agents that is, wants to try these people before a military commission. It's very, very problematic," he continued.As part of Americas "War on Terror" following the September 11 attacks, the CIA began whats known as a "black sites" program. They operated these secret sites between 2002 and 2008. Arie Perliger is a professor and director of security studies at the University of Massachusetts-Lowell. She told us how these sites became places to torture suspected terrorists, including the five we mentioned earlier. "The Black sites system was basically a collection of sites that were, which in many cases were actually run by foreign intelligence organizations or foreign militaries in collaboration with the American intelligence agencies in order to interrogate, in order to detain, to put pressure on individuals that were associated or at least were perceived as associated with those terrorist organizations," Perliger said. "9/11 was a traumatic event to the American intelligence community. And in many ways, also to the U.S. government. It was very clear that we have substantial deficiencies in understanding the landscape of Jihadi extremism and terrorist organizations in general. And in order to address those deficiencies, the government basically provided a lot of freedom and a lot of flexibility