Last Wednesday, during an afternoon of unnerving sleet and rain, I went to see a woman whom the US Government appears to regard as one of its most dangerous citizens. "Hello dear," said Lynne Stewart, who is 65 and was wearing a red dress, as she showed me into the Broadway office where she carried out some of the terrorist-related dealings that have left her facing the rest of her life in jail.

Nearly two months ago, Ms Stewart, a lawyer who has acted for many unpopular causes over the last 30 years, was found guilty by a New York jury of five counts of defrauding the government, conspiracy, and providing material support to terrorism. Ms Stewart will be sentenced on July 15 and could face up to 30 years in prison. "It's mind boggling," she says.

Ms Stewart's story, which has split America's post-Patriot Act legal community, goes something like this: as the court-appointed lawyer for Sheikh Omar Abdel Rahman, a blind Egyptian cleric convicted in 1995 for his part of a conspiracy to blow up the World Trade Center and a series of offices and tunnels in New York, Ms Stewart was one of the only people allowed to visit the Sheikh in prison in Minnesota.

Because the Sheikh retains enormous support among his followers in Al-Gama'a al-Islamiyya or "The Islamic Group", one of Egypt's most violent extremist organizations, strict rules limit his contact with the outside world. These rules, drawn up by the Federal Bureau of Prisons, are known as Special Administrative Measures, or SAMs and, as the Sheikh's attorney, Ms Stewart agreed to obey them.

But then, in May 2000, she broke them. Ms Stewart called a Reuters journalist in Egypt to release a letter from the Sheikh, which said he was withdrawing his personal support for a ceasefire that The Islamic Group had signed with the Egyptian Government in 1997. When asked why she did it, Ms Stewart has argued that keeping the Sheikh visible and politically active was part of a long-term plan to have him returned to Egypt to serve his sentence.

Within days, the Sheikh's withdrawal had been picked up by CNN and Al-Jazeera, a couple of wire services and Al Hayat, the London-based Arabic newspaper, but then the story died down. The ceasefire remained intact.

A month after the news stories, Ms Stewart received a phone call from the Justice Department, who told her off for breaking the rules and refused to let her see the Sheikh. Then, after re-signing a modified set of SAMs in October 2001, Ms Stewart was allowed to resume her visits.

"In my mind it was resolved at that point," said Ms Stewart. "It was like an immediate reaction and then it was a 'Oh, this is not going to be a big deal after all, if they're saying you can go back if you just sign on again.' So then, of course, in 2002, to be arrested for it was quite a shock."

Ms Stewart, along with her translator and one of the Sheikh's followers who had visited the prison with them, was arrested on the morning of April 9 2002. FBI agents spent the day searching her house and offices and Attorney General John Ashcroft flew to New York, first to announce the capture of the Sheikh's "associates" and then to appear on the David Letterman show.

"It was a little bizarre," said Ms Stewart, of the moment when she realised what she had been charged with and the penalties she faced. "I thought … the Government's run out of gas. They've got all this terrific law and they've got nothing to show for it."

The first indictment against Ms Stewart was thrown out by a judge for being too vague but, at the second attempt, she and her colleagues were charged and their trial started in May 2004. Ms Stewart tried to have her case heard separately - mainly because one of her co-defendants, Ahmed Abdel Sattar, was one of the Sheikh's most fervent supporters in the US - but her motion was denied.

Jury selection started the day that the 9/11 Commission was in town, and for the next seven months, a wide range of evidence was introduced to the trial, including a lengthy, eyewitness account of the 1997 Luxor tourist massacre, carried out by The Islamic Group, and an Osama Bin Laden tape which was played three days before the third anniversary of 9/11. The USS Cole bombing of October 2000 was also described. In the prosecutors' summations, there were more than fifty references to killing Jews, because Mr Sattar had once advocated it in a piece of propaganda for The Islamic Group.

After three weeks of deliberations, all the defendants were found guilty on all charges. "The verdict was not unlike being hit by a truck," said Ms Stewart.