Jose Padilla, a US citizen, has been convicted of plotting to kill people overseas and of supporting terrorism.
Jose Padilla was held as an "enemy combatant" for three years
But he first gained notoriety when he was arrested on suspicion of plotting a "dirty bomb" attack inside the US.
Of Puerto Rican origin, he was arrested at Chicago's O'Hare airport in May 2002 after stepping off a flight from Pakistan.
He was then held as an "enemy combatant" in military detention for more than three years.
His eventual indictment in 2005 on charges of conspiracy to "murder, kidnap and maim" people overseas avoided a Supreme Court battle over how long the US government could hold one of its citizens without charge.
The case was transferred to civilian jurisdiction in 2006 and came to court in May 2007.
Padilla has never been charged in relation to the alleged plot to detonate a radioactive bomb.
Padilla and his two co-defendants all denied the charges against them but, after a three-month trial in Miami, jurors took only a day-and-a-half to find all three guilty in August 2007.
The trial of Padilla and two others in Miami lasted for three months
They were convicted of conspiracy to murder, kidnap and maim; conspiracy to provide material support for terrorism; and providing material support for terrorism.
Prosecutors told the court Padilla had travelled to Afghanistan in 1998 to train with the al-Qaeda terror network and that his fingerprints had been found on what they called an al-Qaeda application form.
His defence lawyers insisted he had travelled to Egypt to study Arabic and Islam.
The court also heard FBI recordings of telephone conversations in Arabic between the defendants, containing, according to the prosecution, coded references to terrorist activity.
Padilla's voice was heard on only seven of the tapes and he did not use any coded language, the FBI testified.
Also known as Abdullah al-Muhajir, Jose Padilla had a number of run-ins with the authorities before achieving fame - or infamy - as the dirty bomb suspect.
He was arrested in Florida in 1991 over a road-rage shooting incident and spent a year in a Florida jail.
He completed his probation for aggravated assault and firing a weapon in August 1993.
Prior to that, Padilla had a number of gang-related encounters with police in Chicago - where his family had moved from New York City when he was four years old.
Neighbours quoted in the US press remember Brooklyn-born Padilla as "a nice kid who always helped his mother".
His juvenile record is sealed, but US media reported that as a teenager he started to get into trouble when he joined the Latin Kings, a Chicago street gang.
He is also alleged to have been implicated in a gangland murder when he was 13 and was confined as a juvenile offender in Illinois in 1985.
The young Jose was brought up as a Roman Catholic, and some reports say he converted to Islam while in jail.
Others say that he did so sometime in the mid-1990s, when he was living near Fort Lauderdale, Florida.
He is believed to have married an Egyptian woman.
He apparently dropped out of view after leaving the US in 1998. This, US officials said, was when he first visited Afghanistan.
In 2001, officials said, he made contact with Abu Zubaydah, a senior al-Qaeda commander who is in American custody and apparently co-operating with the FBI.
The US authorities alleged that al-Qaeda asked Padilla to go to Lahore in Pakistan, where he learnt how to make a dirty bomb and allegedly met several other al-Qaeda members.
There was no word on whether these meetings took place before or after the 11 September attacks on the US.
He was 31 at the time of his arrest on 8 May 2002.